Pulse oximetry-based cardio-pulmonary resuscitation (CPR) quality feedback systems and methods

ABSTRACT

Medical devices, plug-ins, systems, and methods for CPR quality feedback are disclosed. The medical devices can calculate peripheral circulation relevant parameters based on measured signals containing at least partial hemodynamic characteristics. Amplitude and area characteristics included in the peripheral circulation relevant parameters can further be determined for providing feedback and control relating to CPR quality during the compression process. Also, compression interruption during CPR can be evaluated based on a pulse waveform generated from the measured signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/927,879, filed Mar. 21, 2018, which is a continuation of U.S. patentapplication Ser. No. 14/497,209, filed Sep. 25, 2014, which claims thebenefit of Chinese Patent Application No. 201310474008.7, filed Oct. 11,2013, and Chinese Patent Application No. 201410208903.9, filed May 16,2014, all of which are hereby incorporated by reference.

TECHNICAL FIELD

This disclosure relates to medical devices, and in particular, tomedical devices and their plug-ins for cardio-pulmonary resuscitation(CPR), as well as CPR quality feedback methods and systems.

BACKGROUND

Cardiovascular disease has become a leading cause of global morbidityand mortality that annually results in 17 million deaths worldwide, manyof which are caused by cardiac arrest. CPR is one of the most commonlyused medical procedures for treating cardiac arrest. CPR may generateblood flow by directly increasing a patient's intrapleural pressure(chest compression mechanism) or by directly compressing the heart(heart pump mechanism) so that some life-sustaining blood flow can bemaintained to the brain and other vital organs.

The 2010 American Heart Association Guidelines for CPR & ECC emphasizedthat a key to the successful resolution of a patient in cardiac arrestis to perform high-quality CPR as early as possible. High-quality CPR isdefined as a compression frequency of at least about 100 times perminute and a compression depth of at least about 5 cm. Even with suchhigh-quality CPR, however, cardiac output (CO) may reach about ¼ or ⅓ ofnormal CO. In clinical practice, manual or mechanical compression isoften used. However, both methods are commonly associated withinsufficient compression frequency and/or depth which can lead to poorCPR. Therefore, in the process of cardiac resuscitation, the CPR qualityshould be monitored. Although the CPR Guidelines recommend end-tidalcarbon dioxide (ETCO₂) and invasive blood pressure monitoring fordetermining CPR quality, these methods require either additionalspecialized medical devices (ETCO₂) or time-consuming procedures(invasive monitoring) which make them less practical for routineclinical practice.

High-quality CPR should also involve little compression interruption. In2013, the AHA recommended that compression time should amount to atleast about 80% of an emergency treatment process. During this process,however, compression interruption may often occur due to endotrachealintubation, rescuer changeover and/or electric defibrillation. Moreover,too much compression interruption will bring about reduction in bothcoronary perfusion pressure and restoration rate of spontaneouscirculation (and even in forward neurofunction prognosis after restoringthe spontaneous circulation). Until now, there has been no monitoringmeans convenient for reminding the rescuer of the compressioninterruption situation. Although blood oxygen monitoring can show pulseoximetry waveforms caused by compression for a patient exhibitingcardiac arrest, judgment is still required as to whether there iscompression interruption by manually observing the pulse oximetrywaveforms, and it is impossible to measure the compression interruptiontime early enough for a warning.

SUMMARY

In one aspect, a medical device includes an optical transceiver, adigital processor and an output module. The optical transceiver includesa light emitting tube and a receiving tube. The light emitting tube canemit at least one light signal to penetrate through human tissue, andthe receiving tube can then receive the at least one light signal andconvert the at least one light signal into at least one electricalsignal. The digital processor may convert the at least one electricalsignal into at least one digital signal and process the at least onedigital signal to obtain peripheral circulation relevant parameters. Theat least one digital signal includes at least partial hemodynamiccharacteristics. The output module can output associated informationcorresponding to the peripheral circulation relevant parameters.

In some embodiments, the peripheral circulation relevant parameters maybe related to a pulsatile perfusion characteristic(s) of the humantissue. In some embodiments, during CPR, the peripheral circulationrelevant parameters can include peripheral circulation parametersrelated to CPR quality.

In some embodiments, the peripheral circulation parameters related toCPR quality may include a first reflecting parameter that can reflectfrequency variation characteristics of CPR compression, a secondreflecting parameter that can reflect depth variation characteristics ofCPR compression, and/or a third reflecting parameter that can reflectcomprehensive variation characteristics of frequency and depth of CPRcompression.

In some embodiments, the digital processor may obtain the peripheralcirculation parameters related to CPR quality by identifying real-timepulsatile perfusion characteristics reflected by the at least onedigital signal. The real-time pulsatile perfusion characteristic can beobtained by identifying fluctuant components and constant components inthe at least one digital signal.

In some embodiments, the digital processor may obtain the firstreflecting parameter by identifying a fluctuant component of the atleast one digital signal and calculating frequency of the fluctuantcomponent.

In some embodiments, the digital processor may obtain the secondreflecting parameter by identifying a fluctuant component of the atleast one digital signal and calculating amplitude conversion on thefluctuant component. In some other embodiments, the digital processormay obtain a corrected second reflecting parameter by identifying afluctuant component and a constant component of the at least one digitalsignal and calculating an amplitude ratio of the fluctuant component andthe constant component after calculating amplitude conversion on thesetwo components.

In some embodiments, the digital processor may obtain the thirdreflecting parameter by identifying a fluctuant component of the atleast one digital signal and calculating an area integral to thefluctuant component. In some other embodiments, the digital processormay obtain a corrected third reflecting parameter by identifying afluctuant component and a constant component of the at least one digitalsignal and calculating an area ratio between an area integral to thefluctuant component and an area integral to the constant component.

In some embodiments, the digital processor can process the at least onedigital signal by at least one analysis method to obtain the peripheralcirculation relevant parameters reflecting CPR quality. The at least oneanalysis method can include a time domain analysis method and/or afrequency domain analysis method.

In some embodiments, the time domain calculation method can be based onidentifying a fluctuant component and a constant component of the atleast one digital signal.

In some embodiments, the time domain analysis method can calculate theperipheral circulation relevant parameters by identifying frequencycharacteristic, amplitude characteristic and/or area characteristic ofthe at least one digital signal, and the frequency domain analysismethod can be used for frequency spectrum identification based on anon-zero frequency spectrum or used for frequency spectrumidentification based on a ratio between a non-zero frequency spectrumand a zero-frequency spectrum.

In some embodiments, the time domain analysis method may identify theamplitude characteristic and the area characteristic of the at least onedigital signal based on the fluctuant component of the at least onedigital signal or based on a ratio between the fluctuant component andthe constant component of the at least one digital signal.

In some embodiments, the associated information can include one or moreof the following information: video information, audio information andlight information which correspond to the peripheral circulationrelevant parameters.

In some embodiments, the output module can be a display module todisplay the video information. The video information may include atendency chart which can reflect dynamic variations of the peripheralcirculation relevant parameters. The video information on the tendencychart may include target range information on the peripheral circulationrelevant parameters which are related to standard CPR quality; a firstwarning when the peripheral circulation relevant parameters exceed theirtarget range; and a second warning when the dynamic variations of theperipheral circulation relevant parameters exceed their optimalvariation range.

In some embodiments, the audio information may refer to auditory sensebased on sound variation, and the light information may refer to visualsense based on light frequency.

In another aspect, a medical device plug-in can include an enclosurecomponent, a signal acquisition interface, a signal processing moduleand an interactive interface. The signal acquisition interface can bepositioned on an external surface of the enclosure component andconnected with signal acquisition accessories. The signal processingmodule positioned in the enclosure component can obtain acquisitionsignals through the signal acquisition interface, convert theacquisition signals into digital signals, and obtain peripheralcirculation relevant parameters through calculation based on the digitalsignals. The interactive interface can recognize the informationinteraction between a host and the signal processing module. The digitalsignals include at least partial peripheral circulation characteristics.

In some embodiments, the enclosure component may protect the signalprocessing module from being damaged by external interferences. Theexternal interferences can include impact of light, and electromagneticand external forces.

In some embodiments, the signal processing module can comprise a signalsampling circuit, a digital processor and a data communication circuit.The signal sampling circuit can obtain the electrical signals from thesignal acquisition interface and convert the electrical signals intodigital signals. The digital processor can then calculate the peripheralcirculation relevant parameters based on the digital signals.

In some embodiments, an operating mode of the interactive interface andthe signal processing module can be at least partially controlled by thehost. The signal processing module may automatically adjust itsoperating mode according to host settings. The signal processing modulemay automatically transmit the peripheral circulation relevantparameters obtained through calculation to the host according to hostsettings.

In some embodiments, operation of the interactive interface and thesignal processing module can rely on energy supply from the host.

In some embodiments, during CPR, the peripheral circulation relevantparameters can include peripheral circulation parameters related to CPRquality, which can include a first reflecting parameter to reflectfrequency variation characteristics of CPR compression, a secondreflecting parameter to reflect depth variation characteristics of CPRcompression, and a third reflecting parameter to reflect comprehensivevariation characteristics of frequency and depth of CPR compression.

In some embodiments, the CPR quality can be reflected throughfluctuation characteristics and the stability level of the peripheralcirculation relevant parameters as well as conformity of the peripheralcirculation relevant parameters with their target range.

In still another aspect, a CPR quality feedback method may includeprocessing one or more of at least two measured signals to calculateperipheral circulation relevant parameters. This method may furtherinclude confirming pulsatile perfusion signals according to the measuredsignals, calculating the peripheral circulation relevant parametersaccording to the pulsatile perfusion signals and displaying theperipheral circulation relevant parameters on a display interface.

In yet another aspect, a CPR quality feedback method may process one ormore of at least two measured signals to calculate peripheralcirculation parameters related to CPR quality based on the measuredsignals. The peripheral circulation parameters related to CPR qualitycan include one or more of the following parameters: a first reflectingparameter, a second reflecting parameter and a third reflectingparameter. The first reflecting parameter may reflect frequencyvariation characteristics of CPR compression, the second reflectingparameter may reflect a depth variation characteristics of CPRcompression, and the third reflecting parameter may reflectcomprehensive variation characteristics of frequency and depth of CPRcompression.

In still another aspect, a medical device can include a blood oxygenprobe, a blood oxygen module and an output module. The blood oxygenprobe can probe measured positions of a test subject and detect bloodoxygen signals of the test subject in real time. The blood oxygen modulecan acquire the blood oxygen signals outputted from the blood oxygenprobe, generate a pulse oximetry waveform based on the blood oxygensignals, calculate peripheral circulation parameters related to CPRquality based on the pulse oximetry waveform, and output associatedinformation on the peripheral circulation parameters related to CPRquality. The output module can provide feedback on the associatedinformation outputted by the blood oxygen module on the peripheralcirculation parameters related to CPR quality.

In some embodiments, the peripheral circulation parameters related toCPR quality may include blood oxygen frequency characteristics of thepulse oximetry waveform and peripheral circulation parameters generatedby compression. The peripheral circulation parameters generated bycompression may include amplitude characteristics of a single pulse waveand/or area characteristics of a single pulse wave.

In some embodiments, the blood oxygen module can separate a constantcomponent and a fluctuant component from the pulse oximetry waveform andcalculate the blood oxygen frequency characteristic and the peripheralcirculation parameters generated by compression based on the fluctuantcomponent of the pulse oximetry waveform or a ratio between thefluctuant component and the constant component of the pulse oximetrywaveform.

In some embodiments, the output module can be a display module todisplay a waveform graph of the amplitude characteristic and/or the areacharacteristic on a display interface. The display module can furtherdisplay an amplitude distribution range limit and/or an areadistribution range limit related to a standard value of chestcompression quality on the waveform graph of the amplitudecharacteristic and/or the area characteristic.

In some embodiments, the blood oxygen module can calculate a fluctuatingvalue of the amplitude characteristic, evaluate whether the fluctuatingvalue of the amplitude characteristic is less than a first preset valueand whether the amplitude characteristic falls within an amplitudedistribution range limit, and, if so, the blood oxygen module may outputa first prompt message to inform a user that current compression qualityhas reached the standard, threshold, or selected limit.

In some embodiments, the blood oxygen module can calculate a fluctuatingvalue of the area characteristic, evaluate whether the fluctuating valueof the area characteristic is less than a second preset value andwhether the area characteristic is within an area distribution rangelimit, and, if so, the blood oxygen module may output a second promptingmessage to inform a user that current compression quality has reachedthe standard.

In some embodiments, the amplitude characteristic can include anabsolute amplitude value or an amplitude index, and the areacharacteristic can include an absolute area value or an area index. Theamplitude index can be a ratio between the absolute amplitude value of asingle pulse wave of the fluctuant component of an amplified pulseoximetry waveform and corresponding DC value of the amplified pulseoximetry waveform. The area index can be a ratio between the absolutearea value of a single pulse wave of the fluctuant component of anamplified pulse oximetry waveform and corresponding DC component of theamplified pulse oximetry waveform.

In some embodiments, the medical device may further comprise aninteraction control interface which may be connected with anothermedical device to recognize data communication between these two medicaldevices. The blood oxygen module can adjust configuration and output ofanother medical device through the interaction control interface. Theconfiguration and output may include one or more of compression depth,compression frequency and compression time phase.

In some embodiments, that another medical device or equipment can be aCPR instrument.

In some embodiments, the medical equipment can also include a controlmodule. The control module can have a signal connection with theinteraction control interface and the blood oxygen module, and may atleast operate to control the compression frequency and the compressiondepth of that another medical equipment. The blood oxygen module mayalso calculate a fluctuating value of the amplitude characteristic,evaluate whether the fluctuating value of the amplitude characteristicis less than a first preset value and whether the amplitudecharacteristic falls within an amplitude distribution range limit. Ifthe fluctuating value of the amplitude characteristic is less than thefirst preset value but the amplitude characteristic does not fall withinthe amplitude distribution range limit, the blood oxygen module mayoutput a first result information to the control module, and the controlmodule can notify that another medical equipment to increase thecompression depth according to the first result information.

In some embodiments, the control module can have a signal connectionwith the interaction control interface, the blood oxygen module and theoutput module, and can at least operate to control the compressionfrequency and the compression depth of that another medical equipment.The blood oxygen module can also calculate a fluctuating value of thearea characteristic, evaluate whether the fluctuating value of the areacharacteristic is less than a second preset value and whether the areacharacteristic falls within an area distribution range limit. If thefluctuating value of the area characteristic is less than the secondpreset value but the area characteristic does not fall within the areadistribution range limit, the blood oxygen module may output a secondresult information to the control module, and the control module cannotify that another medical equipment to increase the compression depthaccording to the second result information. If the area characteristicfalls within the area distribution range limit and the fluctuating valueof the area characteristic is less than the second preset value, theblood oxygen module may output a third result information to the controlmodule, and the control module can notify that another medical equipmentto increase the compression depth according to the third resultinformation and provide feedback on increasing the compression depth tothe blood oxygen module. Based on this feedback, the blood oxygen modulecan calculate the area characteristic of single pulse wave afterincreasing the compression depth and evaluate whether the areacharacteristics of a single pulse wave after increasing the compressiondepth is at a maximum value. If not, the blood oxygen module may outputa fourth result information; if so, the blood oxygen module may output afifth result information. The control module can notify that anothermedical equipment to increase the compression depth according to thefourth result information, or control that another medical equipment tomaintain the current compression depth according to the fifth resultinformation. In some other embodiments, the blood oxygen module may alsooutput a third prompt message when the area characteristic of a singlepulse wave after increasing the compression depth is at the maximumvalue. The third prompt message can inform the user that the testsubject has reached an optimal compression state of stroke volume.

In some embodiments, the blood oxygen module is capable of obtaining apulse waveform comprising one or more single pulse waves based onfluctuant components that are separated from the pulse oximetrywaveform, and then counting a disappearing period of the pulse wave byevaluating a characteristic variation of one or more pulse waves.

In some embodiments, the blood oxygen module can count the duration ofthe disappearing period of the pulse wave and/or calculate a total timepercentage of the disappearing period of the pulse wave.

In some embodiments, the blood oxygen module is also capable of countinga compression period in which the pulse wave is generated. The bloodoxygen module can count duration of the disappearing period of the pulsewave and/or a total time percentage of the disappearing period of thepulse wave, and count duration of the compression period and/or a totaltime percentage of the compression period.

In some embodiments, the blood oxygen module may preset a firstthreshold, a second threshold and a third threshold, and prompt awarning when the duration of the disappearing period of the pulse waveis larger than the first threshold, when the total time percentage ofthe disappearing period of the pulse wave is larger than the secondthreshold, and/or when the total time percentage of the compressionperiod is smaller than the third threshold.

In some embodiments, during CPR, peripheral circulation relevantparameters can include peripheral circulation parameters related to CPRquality, where the peripheral circulation parameters related to CPRquality may include a first reflecting parameter, a second reflectingparameter and a third reflecting parameter, which may reflect,respectively, frequency variation characteristics, depth variationcharacteristic and comprehensive variation characteristic of frequencyand depth of CPR compression. In some embodiments of this disclosure,the peripheral circulation parameters related to CPR quality may furtherrefer to those parameters obtained based on pulse oxymetry.

In an embodiment, peripheral circulation parameters related to CPRquality can include the frequency characteristic of pulse oximetrywaveforms and peripheral circulation parameters generated bycompression, where the peripheral circulation parameters generated bycompression may include amplitude characteristic of a single pulse waveand/or area characteristics of a single pulse wave.

In some embodiments, the first reflecting parameter can be determined byfrequency identification on measured signals containing at least partialhemodynamic characteristics (for example, pulse oximetry waveforms); thesecond reflecting parameter can be determined by amplitude conversion onthe measured signals containing the at least partial hemodynamiccharacteristics; and the third reflecting parameter can be determined byarea integration of the measured signals containing the at least partialhemodynamic characteristics.

Embodiments of this disclosure can calculate the peripheral circulationrelevant parameters based on the measured signals containing the atleast partial hemodynamic characteristics. By using these parameters,timely feedback on CPR quality can be obtained, including thecompression depth and the compression frequency. Since the signals aremeasured in vitro, it is non-invasive to the patient, so that real-timefeedback on CPR quality can be obtained in a non-invasive manner. Inaddition, when the pulse oximetry waveform is used as the basis forcalculating the peripheral circulation parameters, raw data of oxygensaturation of blood can be calculated, so that additional feedbackdevices may not be needed.

In some embodiments, a pulse oximeter plug-in used for CPR qualityfeedback can be manufactured as an independent pluggable module that maybe used together with bedside equipment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of CPR quality feedback according to anembodiment of this disclosure;

FIG. 2 is a schematic diagram for blood oxygen detection according to anembodiment of this disclosure;

FIG. 3 shows a waveform of original blood oxygen signals;

FIG. 4 shows a waveform of a fluctuant component separated from originalblood oxygen signals;

FIG. 5 is a schematic diagram of providing feedback on peripheralcirculation parameters related to a pulse oximeter in text display modeaccording to an embodiment of this disclosure;

FIG. 6 shows a waveform of amplified blood oxygen signals according toan embodiment of this disclosure;

FIG. 7 is a flow chart of CPR quality feedback according to anotherembodiment of this disclosure;

FIG. 8a is a flow chart of providing pulse oximeter-based feedback onperipheral circulation parameters according to an embodiment of thisdisclosure;

FIG. 8b is a flow chart of providing pulse oximeter-based feedback onperipheral circulation parameters according to another embodiment ofthis disclosure;

FIG. 9a is a schematic diagram showing a distribution range and awaveform of an area index in visual mode according to an embodiment ofthis disclosure;

FIG. 9b is a schematic diagram showing a waveform of an amplitude indexin visual mode according to an embodiment of this disclosure;

FIG. 10 shows a waveform of a fluctuant component including interferencefactors according to an embodiment of this disclosure;

FIG. 11 is a diagram illustrating a spectral distribution of bloodoxygen signals acquired using the frequency domain analysis methodaccording to an embodiment of this disclosure;

FIG. 12 is a structural diagram of a CPR quality feedback systemaccording to an embodiment of this disclosure;

FIG. 13 is a structural diagram of a CPR quality feedback systemaccording to another embodiment of this disclosure;

FIG. 14 is a structural diagram of a medical device according to anembodiment of this disclosure;

FIG. 15 is a structural diagram of a pulse oximeter plug-in according toan embodiment of this disclosure;

FIG. 16 is a block diagram of a blood oxygen module according to anembodiment of this disclosure;

FIG. 17 shows a display interface when spontaneous circulation exists;

FIG. 18 shows a display interface when spontaneous circulationdisappears;

FIG. 19 shows a display interface in a case of low-quality CPR;

FIG. 20 shows a display interface in a case of medium-quality CPR;

FIG. 21 shows a display interface in a case of high-quality CPR;

FIG. 22 is a flow chart for monitoring a compression interruption periodduring the CPR process according to an embodiment of this disclosure;

FIG. 23 shows variations of a manual/mechanical compression stateaccording to an embodiment of this disclosure; and

FIG. 24 is a flow chart for monitoring a compression interruption periodduring the CPR process according to another embodiment of thisdisclosure.

DETAILED DESCRIPTION

This disclosure is further described in detail with reference tospecific implementations and accompanying drawings.

This disclosure provides medical devices, methods and medical deviceplug-ins for CPR quality feedback (control) based on signals containingat least partial hemodynamic characteristics. The signals containing theat least partial hemodynamic characteristics can be obtained byacquiring and converting variation signals of absorbed light that canpenetrate through human tissue such as commonly obtained through pulseoximetry. Real-time pulsatile perfusion characteristics of signals canbe identified by separating their constant component and their fluctuantcomponent. In addition, based on these separated fluctuant components ora ratio between the fluctuant component and the constant component,peripheral circulation relevant parameters can be obtained toextrapolate CPR quality.

Determination of oxygen saturation may include two parts, namelyspectrophotometric determination and blood plethysmography. Thespectrophotometric determination can be performed by using red lightwith a wavelength of about 660 nm and infrared light with a wavelengthof about 940 nm. Oxyhemoglobin (HbO₂) has less absorption for 660 nm redlight and more absorption for 940 nm infrared light, while deoxygenatedhemoglobin (Hb) has more absorption for 660 nm red light and lessabsorption for 940 nm infrared light. When determining oxygensaturation, some biological tissues may first be illuminatedrespectively by red light and infrared light, and the red light and theinfrared light that penetrate through the biological tissue can then bedetected on an opposite side of the biological tissues through aphotoelectric detector. Corresponding electrical signals may beoutputted from the photoelectric detector and a ratio between theinfrared light absorption intensity and the red light absorptionintensity can be calculated so as to determine an oxygenation degree ofhemoglobin, namely oxygen saturation (SaO₂).

When determining blood oxygen saturation, blood perfusion should beprovided. When a light beam transilluminates a peripheral tissue, theattenuation degree of transilluminated light energy detected may berelated to cardiac cycle. At the time of systole, peripheral bloodvolume is maximal, and light absorption intensity reaches a maximumvalue and causes the detected light energy to reach its minimum value.The opposite is true at diastole. Variations of light absorptionintensity reflect variations of blood volume. Varying the blood volumecan change the intensity of transilluminated light energy. Absorption ateach wavelength can be a function of skin color, skin structure, iliacusmuscle, blood and other tissues penetrated by the light. The lightabsorption intensity can be considered as a sum of pulsate absorptionand non-pulsate absorption. The AC component can be caused by pulsatoryarterial blood, while the DC component may be constant absorption causedby the light absorption intensities of non-pulsatory arterial blood,venous blood and tissues. Perfusion index PI is a percentage of AC in DC(PI=AC/DC×100%). The AC component and the DC component are respectivelydescribed as the fluctuant component and the constant componenthereinafter.

The pulse oximetry waveform, referring to a series of data obtained byreal-time acquisition of electrical signals of the red light or theinfrared light that penetrates through the biological tissues, can beused to calculate oxygen saturation. In some cases, such data mayinclude sampling value and time information. Based on the detected redlight and infrared light transmission signals, the pulse oximetrywaveform of red light and the pulse oximetry waveform of infrared lightcan be obtained. Oxygen saturation waveform based on these two pulseoximetry waveforms can also be calculated. The pulse oximetry waveformmay have certain relevancy to CPR quality.

The amplitude and area under the curve (AUC) of the pulse oximetrywaveform may have relevancy to hemodynamic indexes of test subjectsincluding cardiac output (CO) and peripheral tissue perfusion. It isalso discovered that the pulse oximeter amplitude and area under thecurve (AUC) can reflect a peripheral circulation state, and thefrequency of the oximetry waveform can reflect the frequency of chestcompression. In the process of CPR, the peripheral circulation state maydepend on a quality of artificial circulation, while the quality ofartificial circulation may depend on the depth and frequency of chestcompression.

An embodiment of this disclosure describes a CPR quality feedbackmethod, which can calculate peripheral circulation parameters related toCPR quality based on a pulse oximetry waveform and use the calculatedperipheral circulation parameters related to CPR quality to providefeedback on CPR quality. The peripheral circulation parameters relatedto CPR quality can include parameters that may be used to providefeedback on the compression frequency and the compression depth in theCPR process. In this embodiment, the blood oxygen frequencycharacteristic of the pulse oximetry waveform can be used to providefeedback on the compression frequency in the CPR process, while theamplitude characteristic and/or area characteristic of the pulseoximetry waveform can be used to provide feedback on the compressiondepth in the CPR process.

Two data processing methods, namely time domain analysis and frequencydomain analysis, will be described in detail. In an example of thisembodiment, the time domain analysis method can be used for digitalsignal data processing. The flow of the CPR quality feedback is shown inFIG. 1 and may include the following steps (steps 11-16).

Physiological signals (in this case, blood oxygen signals) are detectedin step 11. When performing CPR on a test subject, a blood oxygen probecan be employed to detect a measured position of the test subjectundergoing CPR and to detect the blood oxygen signal of the test subjectin real time. In the embodiment of this disclosure, since the process ofproviding feedback on the CPR quality may involve the blood oxygenfrequency characteristic, the amplitude characteristic and the areacharacteristic of the pulse oximetry waveform, the ratio between redlight and infrared light transmission signals may not be needed.Therefore, either of the pulse oximetry waveforms of red light andinfrared light can be used. For the convenience of illustration, any ofthose two pulse oximetry waveforms is referred to as pulse oximetrywaveform. As shown in FIG. 2 illustrating an embodiment, alight-emitting device 100 is installed on one side of the blood oxygenprobe while a photoelectric detector 101 is installed on the other side.The light-emitting device 100 can be a red light or an infrared lightemitting tube, or it may also include the two emitting tubes (red lightand infrared light emitting tubes). The photoelectric detector 101 mayconvert the detected red light or infrared light that penetrates throughthe arterial blood vessel of the finger into electrical signals.

In step 12, the pulse oximetry waveform can be generated based on theacquired blood oxygen signals. Skin, muscle, fat, venous blood, pigmentand bone have a constant absorption coefficient for red light orinfrared light, while HbO₂ and Hb concentrations in arterial blood flowhave periodic variations with the arterial pulsation of blood, leadingto periodic variations in the intensity of the signals outputted by thephotoelectric detector 101. The original pulse oximetry waveform can beobtained by processing (e.g., by signal amplification and/or filtering)these electrical signals having periodic variations.

In step 13, the constant component and fluctuant component can beseparated from the pulse oximetry waveform. As shown in FIG. 3, theoriginal signals may include the fluctuant component S_(AC) and theconstant component S_(DC). In some cases, factors such as body movementand background light interference may result in a drift of the constantcomponent S_(DC) over time, i.e., its numerical value may not beconstant but can fluctuate with time. The AC component may be related topulsating blood volume. When blood flow is weakest, the blood lightabsorption intensity is at minimum, the transmission signal isstrongest, and the AC signal reaches a maximum value. When blood flow isstrongest, its light absorption intensity is at maximum, thetransmission signal is weakest, and the AC signal reaches its minimalvalue. The DC component may be related to the light transmission throughnon-pulsating tissues such as muscle and bone, and the constantcomponent can be the minimum value of the signal. By using suitabletechnologies such as value averaging, smooth filtering technology,FIR/IIR filtering technology or curve fitting technology, the constantcomponent S_(DC) can be filtered out of the original signals and thefluctuant component S_(AC) can be left for further data processing. Thewaveform of the separated fluctuant component is shown in FIG. 4.

In step 14, the blood oxygen frequency characteristic of the pulseoximetry waveform can be calculated based on its fluctuant component.The fluctuant component S_(AC) may be related to the blood flow, and itsfrequency can be consistent with CPR compression frequency. The formulais as follows:F _(CPR) =f _(S) _(AC)   (1)

Where F_(CPR) represents the CPR compression frequency, f_(S) _(AC)represents the frequency of the fluctuant component S_(AC), and the unitof both is Hertz (Hz).

The frequency of the fluctuant component S_(AC) can be multiplied by 60,so as to obtain the blood oxygen frequency characteristic, namely CPRcompression degree/min (i.e., times per minute). Its formula is asfollows:Deg_(CPR) =F _(CPR)*60=f _(S) _(AC) *60  (2)

Where Deg_(CPR) represents the CPR compression degree/min.

In this step, the blood oxygen frequency characteristic of the pulseoximetry waveform may be calculated based on the fluctuant component. Inanother example, the blood oxygen frequency characteristic can also becalculated based on the original pulse oximetry waveform. Therefore,this step may be exchanged with step 13.

In step 15, the peripheral circulation parameters generated bycompression can be calculated based on the fluctuant component of thepulse oximetry waveform. In an example, the peripheral circulationparameters generated by compression may include the amplitudecharacteristic of a single pulse wave. Since the pulse oximetry waveformcan have periodic fluctuations, the range from a wave hollow to anadjacent wave crest is defined as a single pulse wave in an embodimentof this disclosure. In this step, the absolute amplitude value of thesingle pulse wave can be calculated in response to the single pulse wavesignal of the fluctuant component S_(AC) and then used to evaluate thevariations in compression depth during CPR. The amplitude value can becalculated by using any suitable techniques such as maximum amplitudeselection method (max amplitude), average amplitude selection method(average amplitude) or root mean square method, thereby extracting theabsolute amplitude value of each single pulse wave in the fluctuantcomponent. In this embodiment, the root mean square method may be usedto extract the absolute amplitude value Amp_(CPR) of each single pulsewave in the fluctuant component. The formula is as follows:

$\begin{matrix}{{Amp}_{CPR} = \sqrt{\frac{\sum\limits_{n = 0}^{N - 1}{S_{AC}^{2}(n)}}{N}}} & (3)\end{matrix}$

Where S_(AC)(n) represents the n^(th) sampling data point of a singlepulse wave, and N represents the total data length of a single pulsewave, namely the total sampling point count of a single pulse wave.Amp_(CPR) represents the absolute amplitude value of a single pulsewave, which can reflect the depth change in the CPR compression process.In general, the sampled data is in voltage. Therefore, the unit of suchabsolute amplitude value Amp_(CPR) can be defined as PVA (Pulse OximeterVoltage Amplitude).

In another example, the peripheral circulation parameters generated bycompression, which are related to the hemodynamic effect, may alsoinclude the area characteristic of a single pulse wave. In this step,the absolute area value of a single pulse wave can be calculatedaccording to the single pulse wave signal of the fluctuant componentS_(AC) and used to evaluate the variations of stroke volume in the CPRprocess. The absolute area value of the single pulse wave can becalculated by any suitable techniques such as area integral method,which may be applicable to both continuous and discrete signals. In thisembodiment, based on the features of a fixed sampling frequency of bloodpulse oximetry, the method of point-by-point accumulation integral canbe used to calculate the absolute area parameter. The formula is asfollows:

$\begin{matrix}{{Area}_{CPR} = {\sum\limits_{n = 0}^{N - 1}{S_{AC}(n)}}} & (4)\end{matrix}$

Where S_(Ac)(n) represents the n^(th) sampling data point of a singlepulse wave, and N represents the total data length of a single pulsewave, namely the total sampling point count of a single pulse wave.Area_(CPR) represents the absolute area value of a single pulse wave,which can indirectly reflect the variation of the stroke volume in theCPR compression process. In general, the sampled data is a voltagevalue. Therefore, the unit of such absolute area value Area_(CPR) can bedefined as: PVPG (Pulse Oximeter Voltage Plethysmography), which is alsocalled voltage volume.

Those skilled in the art should understand that the peripheralcirculation parameters related to CPR quality may also include not onlyamplitude characteristics but also area characteristics, both of whichmay be calculated in this step.

The feedback on the peripheral circulation parameters related to CPRquality, which are based on a pulse oximeter, is provided in step 16.The feedback mode can be video and/or audio prompt. For example, thevalues of the calculated parameters may be displayed directly. Thoseparameters can also be first compared with an evaluation standard, theresult of whether such parameters comply with the standard may beobtained, and then the result can be displayed.

The feedback mode may also include text display. As shown in FIG. 5, theblood oxygen frequency characteristic, the single amplitude and thesingle area are displayed.

For the blood oxygen frequency characteristic, the guideline requeststhat, when the compression frequency is at least about 100 times perminute, it may be concluded that the compression frequency quality meetsthe standard or determined limit (this index can be modified as moreclinical application data becomes available). In a clinical CPRapplication process, medical personnel can evaluate whether the CPRcompression frequency meets the standard or determined limit or isstable by observing the stability of the blood oxygen frequencycharacteristic value and/or the pulse rate parameter on a displayinterface. Under the precondition of complying with the specificationsof the guideline, the medical personnel may adjust the CPR compressionfrequency, so that the blood oxygen frequency characteristic can providefeedback and control the CPR compression frequency.

The amplitude characteristic can be used to provide feedback on thecompression depth. In general clinical practice, according to thespecifications of the guideline, when the compression depth reaches atleast about 5 cm, it may be deemed that the compression depth basicallymeets the standard or determined limit (this index can be modifiedaccording to a large amount of clinical application data).Theoretically, Amp_(CPR) should exhibit linear correlation with thecompression depth. When the compression depth is stable, the parametervalues of Amp_(CPR) should be stable with less fluctuation. In aclinical CPR application process, the compression may be unstable at thebeginning stage, and thus the index values of Amp_(CPR) can be unstablewith significant fluctuations. With the stabilization of compressiondepth, the index values of Amp_(CPR) can become relatively stable, i.e.,those values can be maintained within a small range of fluctuations. Insuch case, it may be concluded that the CPR compression depth has metthe standard or determined limit.

The area characteristic can be used to indirectly reflect the strokevolume. Theoretically, Area_(CPR) should exhibit a linear positivecorrelation with cardiac ejection volume in every compression. When thecompression depth is stable and the compression frequency is constant,the parameter value of Area_(CPR) should be stable with lessfluctuation. In a clinical CPR application process, the compressiondepth and the compression frequency may be unstable at the beginningstage, and thus the outputted index values of Area_(CPR) may also havelarge fluctuations, i.e., a large variable range of index values. Whenthe compression depth and the compression frequency become stable, theindex values of Area_(CPR) should also exhibit relatively stablecharacteristics, i.e., the variations in index values should fall withina relatively small range of fluctuations. In this case, it may beconcluded that the CPR effect is stable.

In addition, the stroke volume may indicate a maximum output limit fordifferent patients. When the compression has reached a certain extent,if the stroke volume cannot be improved by increasing the depth andfrequency, it may be concluded that the maximum cardiac output undercompression has been achieved on this patient. According to thischaracteristic, when Area_(CPR) is at a relatively stable state, thetester may make adjustment(s) of depth and frequency and then observethe variations in the parameter values of Area_(CPR). If the parametervalues of Area_(CPR) have reached a maximum value (for example, if itfluctuates within down to about 10% or 5%, or if it no longer increaseswith an increase of compression depth), it may be concluded that anoptimal compression state of stroke volume has been found. Theevaluation standard for the maximum value is a parameter, which can beadjusted according to actual clinical effect.

When the cardio-pulmonary function of the human body has stopped, therespective physiologic differences of the human body may also decreaseaccordingly. At this time, it may be considered that the human bodyenvironment is substantially consistent, while CPR manual interventionhas a relatively stable compression depth and compression frequency.This can provide a basis for establishing the CPR measurement indexes.CPR compression depth and compression frequency can cause variations incardiac output. The compression depth may affect the stroke volume,while the variations in stroke volume can be indirectly reflected as thesingle area variations of the blood oxygen pulse wave and the amplitudevariations of a single blood oxygen pulse wave; the fixed absorption ofretained blood, finger bone and finger tissue may be indirectly embodiedas the DC components of the single pulse signals of the blood oxygenpulse wave. Therefore, the amplitude characteristic and/or the areacharacteristic of a single pulse wave can be used to provide feedback onthe CPR quality.

In such embodiment, the absolute amplitude value of Amp_(CPR) and/or theabsolute area value of Area_(CPR) can be used to measure the CPRimplementation effect based on the absolute value of the signal.According to the trend variation and the stability of the parametervalues of both Amp_(CPR) and Area_(CPR) whether the CPR implementationhas reached an optimal state can be evaluated. However, the absoluteamplitude value of Amp_(CPR) and the absolute area value of Area_(CPR)may be affected by the variations in the drive current of a blood oxygenmodule and thus may not be used for other people in a quantitativemanner (i.e., people may have inconsistent parameter values). Inaddition, according to the characteristics of the blood oxygen system,in order for the sampled blood oxygen signals to fall within ameasurable range, the signal conditions (such as by regulating the drivecurrent) may have to be amplified or reduced, and the pulse oximetrywaveform can then be generated according to the amplified/reduced bloodoxygen signals. The variations in the drive current may result in thevariations in the fluctuant component and the constant component of thesignals to the same degree.

In this embodiment, the blood oxygen signals can be amplified. As shownin FIG. 6, the measurement range is about 0-5V, and the signal in solidline 601 falls within a lower measuring range. In this case, driveregulation can be made so that the signals would fall within areasonable measurement range. For example, after a double driveregulation, the signal in dotted line 602 as shown in the figure islocated at a middle position of the measurement range, the originalfluctuant component AC1 is adjusted to AC2, and the original constantcomponent DC1 is adjusted to DC2. According to the drive characteristic,it is known that: AC2=AC1*2 and DC2=DC1*2. In such case, the flow of theCPR quality feedback method in this embodiment is shown in FIG. 7, whichcan include the following steps 21-27.

The blood oxygen signals of the test subject can be detected in step 21.The detection mode is the same as that of step 11.

The acquired blood oxygen signals may be amplified in step 22.

The pulse oximetry waveform can be generated based on the amplifiedblood oxygen signals in step 23.

The constant and fluctuant components may be separated from the pulseoximetry waveform in step 24.

The blood oxygen frequency characteristic of the pulse oximetry waveformcan be calculated based on the pulse oximetry waveform or its fluctuantcomponent in step 25. The calculation mode is the same as that in step14.

In step 26, the peripheral circulation parameters generated bycompression can be calculated based on the fluctuant components of thepulse oximetry waveform. The peripheral circulation parameters generatedby compression may include the amplitude characteristic and/or the areacharacteristic of a single pulse wave. In this step, in addition to theabsolute amplitude value and/or the absolute area value of a singlepulse wave, an amplitude index of a single pulse wave and/or an areaindex of a single pulse wave may also be calculated.

The amplitude index of a single pulse wave refers to a ratio between theabsolute amplitude value of a single pulse wave and the corresponding DCcomponent, and its calculation formula is as follows:

$\begin{matrix}{{AmpIndex}_{CPR} = \frac{\sqrt{\frac{\sum\limits_{n = 0}^{N - 1}{S_{AC}^{2}(n)}}{N}}}{\left( {\sum\limits_{n = 0}^{N - 1}{S_{DC}(n)}} \right)/N}} & (5)\end{matrix}$

where S_(DC)(n) refers to the n^(th) sampling data point of the DCcomponent, N refers to the sampling number, and AmpIndex_(CPR) refers tothe amplitude index of a single pulse wave. In general, the sampled datais measured in voltage. Therefore, the unit of the amplitude indexAmpIndex_(CPR) can be defined as PVAI (Pulse Oximeter Voltage AmplitudeIndex).

AmpIndex_(CPR) is a quantization parameter which may eliminate theinfluence of the drive regulating factor on the amplitude, reflectingthe variation characteristic of the compression depth, resulting in theremoval of interfering drive regulation input.

The area index of the single pulse wave refers to a ratio between theabsolute area value of the single pulse wave and the corresponding DCcomponent, and its calculation formula is as follows:

$\begin{matrix}{{AreaIndex}_{CPR} = {\frac{{Area}_{CPR}}{\left( {\sum\limits_{n = 0}^{N - 1}{S_{DC}(n)}} \right)/N} = \frac{\sum\limits_{n = 0}^{N - 1}{S_{AC}(n)}}{\left( {\sum\limits_{n = 0}^{N - 1}{S_{DC}(n)}} \right)/N}}} & (6)\end{matrix}$

where AreaIndex_(CPR) refers to the area index of a single pulse wave.In general, the sampled data is in volts. Therefore, the unit of thearea index AreaIndex_(CPR) can be defined as PVPI (Pulse OximeterVoltage Plethysmography Index), also called the voltage volume index.

The area index AreaIndex_(CPR) may reduce the individual difference,remove the interference from drive regulation and thus have soundanti-interference capacity.

In step 27, the feedback on peripheral circulation parameters related toCPR quality, which are based on a pulse oximeter, are provided.

Feedback on the peripheral circulation parameters related to CPR qualitycan be provided in other embodiments, or can be provided as describedbelow.

The amplitude characteristic can be related to the compression depth,while the area characteristic can be related to the compression depthand the compression frequency. The guideline has certain specificationson the compression depth and the compression frequency. When suchspecifications are met, it can be concluded that the CPR quality hasreached the standard or determined limit. If the tester can find themapping values of the amplitude characteristic and the areacharacteristic which correspond to the basic standard values specifiedin the guideline, the amplitude characteristic and the areacharacteristic can be directly compared with their mapping values so asto evaluate whether the CPR quality basically meets the standard ordetermined limit. These mapping values constitute distribution rangelimits of the amplitude or area characteristics.

Using the area index AreaIndex_(CPR) in the area characteristic as anexample, feedback on whether the CPR quality meets the standard ordetermined limit can be provided by evaluating whether the area indexAreaIndex_(CPR) falls within the distribution range. Feedback on whetherthe CPR quality meets the standard or determined limit can also beprovided according to the fluctuation of the area index AreaIndex_(CPR).The feedback flow as shown in FIG. 8a can include the following steps30-39.

In step 30, distribution range limits of the area index AreaIndex_(CPR)can be obtained (the distribution range limit may be related to therequired CPR implementation quality) so as to determine a distributionrange of the AreaIndex_(CPR) index. This distribution range representsthat, if the area index AreaIndex_(CPR) falls within this range, the CPRimplementation effect can be regarded as acceptable and therefore theCPR implementation reached the standard or determined limit. Thesedistribution range limits can be input in every CPR implementation, orthey can be pre-stored in the system and read from the memory address inevery CPR implementation.

Among the normal population, the distribution range of the stroke volumeis about 4.8-8 L/min. After the cardio-pulmonary function of human bodyhas stopped, as mentioned above, the human body environment is oftenrelatively consistent. About ⅓-¼ of the normal stroke volume can bereached by performing the CPR.

In step 31, the single area index AreaIndex_(CPR) obtained throughcalculation can be processed to generate the waveform data of the singlearea index AreaIndex_(CPR). Such a waveform may be displayed on thedisplay interface. The distribution range limits may also be displayedwith the waveform of the area index AreaIndex_(CPR), so that thedistribution range and the waveform of the area index AreaIndex_(CPR)can be shown in a visual mode as shown in FIG. 9. The distribution rangeof the area index AreaIndex_(CPR) can be determined by the maximum value(“Max”) and the minimum value (“Min”).

In step 32, the single area index AreaIndex_(CPR) can be compared withMin so as to evaluate whether the index reaches the standard ordetermined limit. If the single area index AreaIndex_(CPR) is largerthan Min, it may be concluded that the index reaches the standard ordetermined limit, and then step 33 can be performed. Otherwise, thesingle area index AreaIndex_(CPR) continues to be compared with Min.

In step 33, a fluctuating value of the area index AreaIndex_(CPR) may becalculated. In order to obtain the fluctuating value of the area indexAreaIndex_(CPR) the difference between the area indexes AreaIndex_(CPR)of two adjacent single pulse waves can be calculated.

In step 34, whether the fluctuating value of the area indexAreaIndex_(CPR) is less than a second preset value can be evaluated. Ifso, it may be concluded that the value of the area index AreaIndex_(CPR)is stable and step 35 can be performed. Otherwise, it may be concludedthat the value of the area index AreaIndex_(CPR) is unstable and step 36can be performed.

In step 35, when the fluctuating value of the area index AreaIndex_(CPR)is less than the second preset value, a second prompt message may beoutputted. The second prompt message may be used to inform the user thatthe present compression quality has reached the standard or determinedlimit. The second prompt message may inform the user that thefluctuating value of the present area index AreaIndex_(CPR) is stable,or the present stroke volume is stable, or the present compressionquality (which for example may include some indexes such as compressionfrequency and compression depth) has reached the standard or determinedlimit.

In step 36, when the fluctuating value of the area index AreaIndex_(CPR)is equal to or greater than the second preset value, another promptmessage may be outputted which can be used to inform the user that thepresent compression quality fails to reach the standard, or no promptmessage is outputted.

In practical CPR applications, the medical staff may, according to theAreaIndex_(CPR) index (reasonable interval of the blood oxygen waveformarea), make adjustment(s) to the compression depth and the compressionfrequency under the precondition of complying with the specifications ofthe guideline, thus ensuring that the CPR implementation effect fallswithin the acceptable range, for example, the quantitative indexes ofthe CPR implementation meet the acceptable range. During suchadjustment(s), the medical staff may also search for the maximum valueof the AreaIndex_(CPR) parameter and evaluate whether or not theAreaIndex_(CPR) parameter has some significant variations or remainssubstantially unchanged so as to obtain the optimized CPR implementationeffect. For example, if the AreaIndex_(CPR) parameter does not havenotable variations after adjusting the depth and the frequency, it maybe concluded that an optimal CPR effect has already been achieved.

Additionally, if a CPR instrument is used to deliver compressions, someresult information can be outputted to the CPR instrument, allowing itto auto-regulate. Step 37 may be performed after step 35.

Furthermore, in order to evaluate whether the CPR quality has reached anacceptable state, when the fluctuating value of the area indexAreaIndex_(CPR) is less than the second preset value, a third resultinformation may be outputted in step 35 to a CPR instrument withself-regulation of compression. Step 37 may be performed after step 35.

In step 37, adjustment(s) made on the compression depth can be madebased on the third result information. For example, the compressiondepth may be increased slightly.

In step 38, the area index AreaIndex_(CPR) after increasing thecompression depth can be calculated and a determination of whether thearea index AreaIndex_(CPR) has reached its maximum value can be furtherevaluated. For example, whether the area index AreaIndex_(CPR) increaseswith the increase of the compression depth can be evaluated. If so, itmay be concluded that the present area index AreaIndex_(CPR) has notreached its maximum value. On the other hand, if the area indexAreaIndex_(CPR) does not increase with an increase in compression depth,it may be concluded that the present area index AreaIndex_(CPR) hasreached its maximum value. When the present area characteristic is atthe maximum value, step 39 a can be performed; otherwise, step 39 b maybe performed.

In step 39 a, a fifth result information can be outputted, where thefifth result information may be used to control the CPR instrument in amanner to maintain the present compression depth. A third prompt messagecan also be outputted, where the third prompt message may be used toinform the user that the test subject has reached an optimal compressionstate of stroke volume.

In step 39 b, a fourth result information may be outputted, which can beused to control the CPR instrument to increase the compression depthappropriately or find other causes.

In addition, if the fluctuating value of the area characteristic is lessthan the second preset value but fails to fall within the areadistribution range, a second result information can be outputted, andthe CPR instrument may be commanded to increase the compression depthbased on the second result information.

To observe the waveform graph of the area index AreaIndex_(CPR) a morevisual manner, marks can also made at various wave stages on thewaveform graph. For example, as shown in FIG. 9a , the rising stage 201,the stable stage 202, the unstable stage 203 and the adjustment stage204 can be distinguished by partition markings. When evaluating whetherthe value of the area index AreaIndex_(CPR) is stable, a sliding timewindow 205 may be used, where the fluctuation characteristic of theindex parameter value in the time window 205 can be measured. Forexample, whether the area index AreaIndex_(CPR) in the sliding timewindow 205 is stable can be evaluated. In this figure, the rising stage201 shows the unstable state of the area index AreaIndex_(CPR) in rapidvariation at the beginning of a compression; the stable stage 202 showsthe state with relatively good CPR quality; while the unstable stage 203shows the state with relatively poor CPR quality. When CPR is relativelystable, adjustment(s) can be made to the compression depth to find theindividual maximum cardiac output. At the adjustment stage 204, thevalue of the area index AreaIndex_(CPR) may enter a stable stage. Atthis stage, the medical staff may make further adjustment(s) to thecompression depth. For example, the compression depth can be adjustedfrom about 5 cm at point A to about 6 cm at point B. It can be foundthat, A and B have a consistent influence effect on the parameter index.Thus, it may be concluded that the maximum cardiac output has beenachieved under a compression of about 5 cm. The medical staff mayevaluate whether an optimal compression state of the stroke volume hasbeen achieved through a visual diagram. In addition, the system may alsooutput some prompt message to alert the medical staff. For example, whenthe present area characteristic is at the maximum value, the system maymaintain the present compression depth and output the third promptmessage, where the third prompt message can be used to inform the userthat the test subject has reached an optimal compression state of thestroke volume.

For the amplitude characteristic, the feedback processing described insteps 30-39 can also be used. That is, the mapping value of amplitudecharacteristic corresponding to “compression depth ≥5 cm” can be firstestablished, which mapping value constitutes an amplitude distributionrange limit. On the display interface, the system may display thewaveform graph of the amplitude characteristic and the amplitudedistribution range limit related to the standard value of cardiaccompression depth on the waveform graph, thereby showing a distributionrange of the amplitude characteristic in visual mode. By observingwhether the amplitude characteristic falls within the amplitudedistribution range limit, the medical staff may evaluate whether thecompression depth reaches the standard or determined limit.

In the embodiment shown in FIG. 8b , the fluctuating value of theamplitude characteristic can be calculated according to the amplitudecharacteristic of a single pulse wave, and then whether the fluctuatingvalue of the amplitude characteristic is less than the first presetvalue and whether the amplitude characteristic falls within theamplitude distribution range limit can be evaluated. If so, the systemmay output the first prompt message, where the first prompt message canbe used to inform the user that the present compression depth hasreached the standard or determined limit. If the fluctuating value ofthe amplitude characteristic is less than the first preset value but theamplitude characteristic does not fall within the amplitude distributionrange limit, the system may output the first result information, andcommand the CPR instrument to increase the compression depth based onthe first result information.

To observe the waveform graph of the amplitude index in a more visualmanner, marks can also be made at various wave stages on the waveformgraph. For example, as shown in FIG. 9b , the rising stage 301, theunstable stage 302, the stable stage 303 and the alarm stage 304 may bedistinguished by partition marking. As shown in FIG. 9b , a sliding timewindow 305 can be established and the fluctuation characteristic of theindex parameter value in the time window 305 can be measured. The risingstage 301 in this figure shows the rapid variation of the indexparameter at the beginning of compression. If there is significantfluctuation as shown by the unstable stage 302 in the figure, the systemmay indicate that the compression depth is unstable and the compressionstate should be adjusted. If the index parameter values shown by thestable stage 303 are stable with a difference not exceeding about ±5%(±5% refers to the proportion of the D-value of fluctuations in theaverage value in the time window, which can be independently adjustedaccording to actual needs), it may be concluded that the compressiondepth is stable. According to the specifications of CPR guidelines, thecompression depth should be at least about 5 cm. If the mean compressiondepth in the sliding time window is less than the limit corresponding toabout 5 cm, the system can display the alarm stage 304 and warn themedical staff to increase the compression depth.

Frequency domain analysis method is used to process the data in anotherembodiment, which can be the difference between this embodiment and theabove-described embodiments.

During CPR, there may be many interference factors such as thevibrations generated by a compression, the vibrations of chest cavity,and the impact of medical devices. In FIG. 10, an example of thewaveform graph of the separated fluctuant component is shown. Due tothese factors, the parameters obtained by the above-described method maybe distorted. Since there can be energy conservation for the signalbetween a domain and its corresponding transform domain as demonstratedin formula 6 (below), those above-described parameters should beestablished based on the frequency domain analysis technique.

$\begin{matrix}{{\sum\limits_{n = 0}^{N - 1}{❘{S_{AC}(n)}❘}^{2}} = {\frac{1}{M}{\sum\limits_{k}^{M - 1}{❘{X(k)}❘}^{2}}}} & (7)\end{matrix}$

where X(k) represents the amplitude value of each frequency spectrumcomponent, and M represents the M frequency spectrum components existingin the frequency spectrum.

Spectrum analysis can be performed on the blood oxygen signal to obtaina spectral distribution diagram. As shown in FIG. 11, the frequency f₁is the main frequency or the fundamental frequency and is consistentwith the CPR compression frequency. In addition to the main frequency,there may be several double frequencies. For example, f₂ and f₃ aredouble frequencies in FIG. 11. These main and double frequencies arereferred to as the effective frequency components of the signal. Asshown in FIG. 11, fq is the interfering frequency. In this embodiment,formula (6) can be used to calculate the signal frequency spectrum atthe positions of the effective frequency components (including the mainfrequency f₁ and the double frequencies f₂, f₃ . . . f_(N)) so as toobtain the corresponding evaluation indexes. For an uninterrupted steadysignal, the effective value of the signal calculated through the timedomain method should be equal to that calculated through the frequencydomain method. However, in real applications, the frequency domainmethod often has better anti-interference capacity.

In one embodiment, the frequency domain analysis method can be used tocalculate the blood oxygen frequency characteristic as well as theamplitude characteristic and the area characteristic of a single pulsewave.

The blood oxygen frequency characteristic of the pulse oximetry waveformcan be calculated. f₁ represents the main frequency of the fluctuantcomponent of S_(AC) and this frequency is consistent with the CPRcompression frequency. When this frequency is multiplied by 60, theresult is the blood oxygen frequency characteristic, namely CPRcompression degree/min.F _(CPR) ^(*) =f ₁  (8)Deg_(CPR) ^(*) =F _(CPR) ^(*)*60=f ₁*60  (9)

where F_(CPR) ^(*) represents the CPR compression frequency, f₁represents the signal frequency, and Deg_(CPR) ^(*) represents the CPRcompression degree/min with a unit of times per minute.

In clinical CPR application, whether the CPR compression frequency isstable can be evaluated by observing the stability of Deg_(CPR) ^(*)index or pulse rate parameter. Under the precondition of complying withthe specifications of the guideline, manual operation or automationdevice can be used to adjust the CPR compression frequency. In generalclinical applications, when the compression frequency is at least about100 degrees/min, it may be concluded that the compression frequencyquality has reached the standard or determined limit (this index can bemodified according to a large amount of data collected on practicalclinical applications).

The amplitude characteristic of single pulse wave of a pulse oximetrywaveform can be calculated based on the effective frequency component ofthe fluctuant component of S_(AC), so as to evaluate the variations ofthe compression depth in the CPR implementation process. This amplitudecharacteristic can be calculated by using any suitable techniques, suchas maximum amplitude selection method (max amplitude), average amplitudeselection method (average amplitude), or root mean square method (rootmean square). In one embodiment, the root mean square method may be usedto extract the absolute amplitude value Amp_(CPR) ^(*) of all thefrequency components f_(n) (n=1, 2, 3, . . . N) of the fluctuantcomponent of S_(AC). The corresponding formula is as follows:

$\begin{matrix}{{Amp}_{CPR}^{*} = \frac{\sqrt{\sum\limits_{n = 0}^{N - 1}\left( {\sum\limits_{k = 0}^{K - 1}{X_{f_{n}}(k)}^{2}} \right)}}{K}} & (10)\end{matrix}$

where Amp_(CPR) ^(*) represents the absolute amplitude value, krepresents the sampling data point of the current f_(n), K representsthe total data length of the effective main frequency f_(n), and nrepresents the n^(th) frequency peak which amounts to N effectivefrequency peaks.

In other examples, the amplitude characteristic of the main frequency f₁can also be used to evaluate the variations of the compression depth inthe CPR implementation process. Amp_(CPR) ^(*) can reflect the depthvariation in the CPR compression process. In theory, Amp_(CPR) ^(*)should exhibit linear dependence with the compression depth. When thecompression depth is stable, the parameter value of Amp_(CPR) ^(*)should be stable with less fluctuations. In clinical CPR applicationprocess, the compression depth may be unstable at the beginning stage,in which case the index value of Amp_(CPR) ^(*) may also be unstablewith significant fluctuations. With the stabilization of the compressiondepth, the index value of Amp_(CPR) ^(*) can become relatively stable.In clinical applications, the CPR guidelines specify that thecompression depth should be at least about 5 cm. In some embodiments,corresponding relations can be established between Amp_(CPR) ^(*) andthe compression amplitude according to a series of animal and humanexperiments, thereby providing a mapping value of Amp_(CPR) ^(*) whenthe compression depth is at least about 5 cm. After Amp_(CPR) ^(*) iscalculated, Amp_(CPR) ^(*) can be compared with the mapping value. IfAmp_(CPR) ^(*) is stable in fluctuation and comparable with this mappingvalue, it may be concluded that the compression depth has reached thestandard or determined limit (this index can be modified based on futureclinical data results).

In order to evaluate the variations of the stroke volume in the CPRimplementation process and indirectly reflect the CPR implementationquality, the area characteristic of a single pulse wave of the pulseoximetry waveform can be calculated based on the effective frequencycomponents of the fluctuant component of S_(AC). Any suitabletechniques, such as area integral method (continuous signal and discretesignal), can be used to calculate the area characteristic to obtain thearea information of each pulse wave. In this embodiment, since thesampling frequency is fixed in the blood oxygen technology, the methodof point-by-point accumulation integral may be used to calculate theabsolute area value Area_(CPR)*.

$\begin{matrix}{{Area}_{CPR}^{*} = {\sum\limits_{n = 0}^{N - 1}\left( {\sum\limits_{k = 0}^{K - 1}{X_{f_{n}}(k)}} \right)}} & (11)\end{matrix}$

where Area_(CPR) ^(*) represents the absolute area value of single pulsewave which corresponds to the parameter related to the stroke volume andis also referred to as voltage volume, n represents the currenteffective frequency component f_(n), N represents the total number ofthe effective frequency components, k represents the sampling data pointof the current effective frequency f_(n), and K represents the totaldata length of the effective frequency component f_(n).

Area_(CPR) ^(*) can be used to indirectly reflect the stroke volume. Intheory, Area_(CPR) ^(*) should exhibit linear positive correlation withthe cardiac ejection volume in every compression. When the compressiondepth is stable and the compression frequency is constant, the parametervalue of Area_(CPR) ^(*) should be stable with small fluctuations. Inclinical CPR application process, the compression depth and thecompression frequency may be unstable at the beginning stage, and thusthe outputted index value of Area_(CPR) ^(*) may also have largefluctuations, namely a large variation range of index values. When thecompression depth and the compression frequency are stable, the indexvalues of Area_(CPR) ^(*) should also exhibit relatively stablecharacteristics, namely the variations in index value should fall withina relatively small range of fluctuations. Once this happens, the strokevolume may have reached its maximal output limit. When the compressionshave reached this point, the stroke volume may not be improved byincreasing the depth and the frequency. According to thischaracteristic, when Area_(CPR) ^(*) is in a relatively stable state,the medical staff may make adjustment(s) to the depth and the frequencyand then observe the variations of Area_(CPR) ^(*) parameter index. Ifthe parameter value changes slightly (for example, the variation is lessthan or equal to about 10%, 5% or any other value set according topractical clinical considerations) or fails to notably increase with theincrease of the compression depth, it may be concluded that Area_(CPR)^(*) has reached the maximum value.

In some embodiments, when applying the frequency domain analysis methodfor data processing, the amplitude index AmpIndex_(CPR) ^(*) of a singlepulse wave and the area index AreaIndex_(CPR) ^(*) of a single pulsewave can be calculated after amplifying/reducing the blood oxygensignals. The calculation formula is as follows:

$\begin{matrix}{{AmpIndex}_{CPR}^{*} = \frac{\frac{\sqrt{\sum\limits_{n = 0}^{N - 1}\left( {\sum\limits_{k = 0}^{K - 1}{X_{f_{n}}(k)}^{2}} \right)}}{K}}{\left( {\sum\limits_{n = 0}^{N - 1}{S_{DC}(n)}} \right)/N}} & (12)\end{matrix}$

where AmpIndex_(CPR) ^(*) represents the amplitude index of a singlepulse wave, which is a ratio between the absolute amplitude value of asingle pulse wave and the corresponding DC component.

AmpIndex_(CPR) ^(*) is a quantization parameter. This parameter canreduce or eliminate the influence of the amplification on the signalamplitude, have sound anti-interference capacity, and visually reflectthe variations of the compression depth.

$\begin{matrix}{{AreaIndex}_{CPR}^{*} = {\frac{{Area}_{CPR}^{*}}{\left( {\sum\limits_{n = 0}^{N - 1}{S_{DC}(n)}} \right)/N} = \frac{\sum\limits_{n = 0}^{N - 1}\left( {\sum\limits_{k = 0}^{K - 1}{X_{f_{n}}(k)}} \right)}{\left( {\sum\limits_{n = 0}^{N - 1}{S_{DC}(n)}} \right)/N}}} & (13)\end{matrix}$

where AreaIndex_(CPR) ^(*) represents the area index of a single pulsewave, which is a ratio between the absolute area value of a single pulsewave and the corresponding DC component.

AreaIndex_(CPR) ^(*) is a quantization parameter. It may reduce orremove the individual difference and the interference caused by signalamplification/reduction and have sound anti-interference capacity.

The above-described steps 31-39 are also applicable to the followingembodiment. When adopting the frequency domain analysis method, the CPRquality can be reflected by the area index and its fluctuation.

In some embodiment, after the fluctuant components are separated fromthe acquired blood oxygen signals, a pulse waveform including one ormore single pulse wave(s) can be generated based on the fluctuantcomponents (step 102). The one or more single pulse wave(s) may furtherbe recognized for compression interruption monitoring during the CPRprocess (step 104).

In the case where the patient has no restoration of spontaneouscirculation, cardiac impulse and thus blood circulation at finger tipsmay be generated by compressing the patient's heart. Once stoppingcardiac compression, the blood circulation may disappearcorrespondingly. That is, the pulse wave can be generated undercompression, and the pulse wave may disappear after stoppingcompression. Therefore, manual/mechanical compression state can berecognized from the pulse wave based on its changes following thecompression. The manual/mechanical compression state herein can includea continuous compression state in which there is continuous pulse wavesignal and a compression interruption state in which the pulse wave maydisappear, where the continuous compression state and the compressioninterruption state may also be called as a pulse state and a pulselessstate.

The pulse wave can be recognized based on amplitude and width of asingle pulse wave. The amplitude as described above can be defined asthe AC component, while the width may correspond to a mapping value ofthe sampling point count of a single pulse wave. The mapping relationamong the sampling point count, the pulse width, and the pulse rate maybe defined as follows:PulseRate=60*f _(HZ)=60*SampleRate/Width  (14)

where PulseRate represents a pulse number per minute (degree/min),f_(HZ) represents the frequency of a single pulse wave, SampleRaterepresents a sampling rate for blood oxygen signal, and Width representsa pulse width for a single pulse wave (i.e., the sampling point count).The area index in the time domain can then be obtained based on thewidth of the single pulse wave.

Typically, the amplitude information and the width information of onesingle pulse wave may be extracted for evaluating whether the singlepulse wave is complete. During clinical emergency treatment, it maybecome more difficult to accurately recognize the pulse wave based onthe amplitude information and the width information of one single pulsewave due to some environmental interference.

In one embodiment, multiple single pulse waves may be used for pulsewave recognition, where a disappearing period of the pulse wave may berecognized based on changes of multiple single pulse waves. In oneembodiment, at least three continuous single pulse waves can beextracted, and then the disappearing period of the pulse wave can berecognized based on area variation and/or shape variation of thesesingle pulse waves.

For the purpose of improving the accuracy in recognizing the pulse wave,more characteristic information can be utilized for auxiliaryrecognition. In one embodiment, area fluctuation and/or shape relevanceamong multiple continuous single pulse waves (e.g., about three) can beused to improve the recognition of the pulse and/or pulseless statesignificantly, thereby reducing the influences from some clinicalinterference.

In a following step 106, the disappearing period of the pulse wave canbe counted based on the recognition result, where such disappearingperiod may correspond to a manual/mechanical compression interruptionperiod. Subsequently, the counting information can be outputted in step108. For example, the counting information can be displayed on a displayscreen.

For the counting operation in step 106, duration of the disappearingperiod of the pulse wave (also called disappearing duration) can becalculated in one embodiment, and/or a total time percentage of thedisappearing period of the pulse wave (also called total time percentageof disappearing duration) can be calculated in another embodiment. Thetotal time percentage of the disappearing period of the pulse wave mayrefer to a ratio between the accumulated duration of the disappearingperiod of the pulse wave and the duration of the CPR operation (alsocalled CPR duration).

In another embodiment, in addition to counting the disappearing durationof the pulse wave, the compression period in which the pulse wave can begenerated (also called compression duration) can also be counted. Thiscompression period refers to an appearing period of the pulse wave. Inthis case, when multiple single pulse waves are used for pulse waverecognition, the compression period in which the pulse wave can begenerated/detected may also be recognized based on changes of multiplesingle pulse waves. Duration of the compression period and/or a totaltime percentage of compression duration can be calculated.

In another embodiment, the counting step may further include presettinga first threshold and a second threshold, and prompting warninginformation when the disappearing duration exceeds the first thresholdand/or when the total time percentage of disappearing duration exceedsthe second threshold.

A total duration, i.e. the duration of the CPR operation, can be countedthrough the following methods in this disclosure. Under defaultsettings, the time-counting operation may be started once the patientwears the blood oxygen probe and the CPR duration may be reset when theblood oxygen probe is not connected to the patient (the blood oxygenprobe is used for acquiring physiological signals from the patient).Alternatively, a start button and a stop button can be provided, and thetime-counting operation may be started and stopped respectively by amedical staff clicking on the start button and the stop button.

At the end of the manual/mechanical compression interruption period, themanual/mechanical compression state may change into the continuouscompression state, and the disappearing duration may be stopped to becounted since the compression waveform can be generated once again.

In one embodiment, the total time percentage of the disappearing periodof the pulse wave can be calculated by a following formula:

$\begin{matrix}{{Interval}_{Ratio}^{CPR} = {\frac{\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}}{\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}}*100\%}} & (15)\end{matrix}$

where

$\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}$represents an accumulated sampling point count during manual/mechanicalcompression, and

$\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}$represents an accumulated sampling point count within amanual/mechanical compression interruption period present in themanual/mechanical compression process (p=1, 2, 3, . . . P, and q=1, 2,3, . . . Q, where p represents a p^(th) manual/mechanical compressioninterruption period, P represents a total number of manual/mechanicalcompression interruption periods present in the manual/mechanicalcompression process having a length of N points, q represents a q^(th)point during the p^(th) CPR interruption period, and Q represents atotal point count of the p^(th) manual/mechanical compressioninterruption period).

In an embodiment, the compression duration can be obtained bysubtracting the disappearing duration from the CPR duration. In anembodiment, the total time percentage of compression duration(Compression_(Ratio) ^(CPR)) can be determined by: 1−Interval_(Ratio)^(CPR). In another embodiment, the counting step may further includepresetting a third threshold and prompting further information when thetotal time percentage of compression duration is smaller than the thirdthreshold.

Based on the accurate recognition of the single pulse wave signal,sliding time window can be used to recognize the manual/mechanicalcompression state in another embodiment.

In step 202, a sliding time window shown by D in FIG. 23 can beconstructed so as to observe a pulse wave state within this window.Duration of the sliding time window can be set according to an actualsituation. For instance, its duration can be about 10 s in defaultsetting.

In step 204, the pulse wave state within the sliding time window can beevaluated, and some other operations may be triggered based on theevaluation result. In view of response speed and stability, featurerecognition can be performed on about three pulse waves, so as todetermine whether the current manual/mechanical compression state is themanual/mechanical continuous compression state or the manual/mechanicalcompression interruption state. As shown in FIG. 23, after performingthe feature evaluation on about three pulse waves, the pulse waves inthe section A (i.e., CPR Duration 1) and the section C (i.e., CPRDuration 2) can be determined to be generated by manual/mechanicalcompression and thus the time counting may not be started for thedisappearing period of the pulse wave in these two states.

In step 206, the time counting can be started for the disappearingperiod of the pulse wave once the sampled signals enter a pulselessstate. Specifically, the disappearing duration can be counted byaccumulating the sampling point count, while the sampling rate withinone single period may correspond to about one second. Therefore, thedisappearing duration (i.e., duration of the manual/mechanicalcompression interruption period) can be counted by seconds. In FIG. 23,the time counting for the CPR compression interruption period may bestarted from the position 1 in section B (i.e., an interval withoutCPR), and then the time-counting information can be sent to a client.When the manual/mechanical compression interruption period ends, thecompression waveforms can be detected once again, the time counting anddisplaying operations for the CPR compression interruption period can bestopped and the disappearing duration may be reset.

In clinical applications, since the feature evaluation is implemented onabout three pulse waves, the sampled data corresponding to the aboutthree pulse waves may be needed for recognizing whether the sampled datais pulseless data and for evaluating whether the currentmanual/mechanical compression state has changed into themanual/mechanical compression interruption state based on therecognition result when the current state changes into the pulselessstate. This may lead to time delay in the time counting & displayingfunctions for the manual/mechanical compression interruption period. Forthat reason, when the manual/mechanical compression state changes fromthe compression interruption state into the continuous compressionstate, the time counting and displaying functions for themanual/mechanical compression interruption period may last for a certaintime before being stopped and reset due to the pulse wave recognitionmethod used in this disclosure. As shown in FIG. 23, the duration of themanual/mechanical compression interruption period may be shown at theposition 2 instead of the position 1. Similarly, when entering sectionC, the duration of the CPR interruption period may still be displayeduntil about three pulse waves are detected.

The time delay of the time counting and displaying functions for themanual/mechanical compression interruption period may depend on thewidth of the recognized pulse wave (i.e., pulse rate). The higher thepulse rate is, the shorter the recognition time becomes, and vice versa.When using about three pulse waves in this disclosure, the responsespeed for recognizing the manual/mechanical compression interruptionperiod may be about 0.6-9 s since a recognizable physiological pulsewave may have a range of [20-300]BPM (which corresponds to a pulse rateof [0.33-5]Hz):

$\begin{matrix}{{Time}_{response} = {\frac{3{Pulse}}{\left\lbrack {0.33{\left. {Hz} \right.\sim 5}{Hz}} \right\rbrack} = \left\lbrack {9{\left. S \right.\sim 0.6}S} \right\rbrack}} & (16)\end{matrix}$

where 3Pulse represents about three pulse periods, and [0.33-5]Hzrepresents the frequencies of the recognizable pulse width.

According to CPR Guidelines, the compression frequency should be atleast 100 degrees/min. Based on the formula described above, theresponse speed may be about 1.64 s; that is, it may take about 1.64 s torecognize the state of the compression waveform in this disclosure. Thisresponse speed can meet the time-sensitive requirements of clinicalapplication, and the compression interruption evaluation can improveboth the accuracy during emergency treatment and the survival rate ofthe patient.

In step 208, warning information may be prompted when duration of thedisappearing period of the pulse wave exceeds the first threshold. It isknown that the patient may be affected physiologically if the CPR isinterrupted for about 10 s. For this reason, the first threshold in thisdisclosure can be set as about 10 s, so that warning information can beprovided when the disappearing duration is larger than 10 s.

In step 210, a total time percentage of the disappearing period of thepulse wave (which corresponds to a total time percentage of CPRinterruption period) can be calculated, and warning information can beprompted if the total time percentage of the disappearing durationexceeds the second threshold (step 212). Alternatively, a total timepercentage of the compression period in which the pulse wave can begenerated/detected may also be calculated. That is, the total timepercentages of both the disappearing period and the appearing period ofthe pulse wave can be considered comprehensively, so as to have higherrecognition accuracy and sensitivity. According to CPR Guidelines, ifthe interruption period accounts for more than 20% of the totalemergency time by manual/mechanical compression, the patient cannot besuccessfully rescued. Therefore, the total time percentage of CPRinterruption period Interval_(Ratio) ^(CPR) can be defined in thisdisclosure to reflect the time percentage feature, where theInterval_(Ratio) ^(CPR) may be calculated according to the followingformula:

$\begin{matrix}{{Interval}_{Ratio}^{CPR} = {\frac{\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}}{\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}}*100\%}} & (15)\end{matrix}$

where

$\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}$represents an accumulated sampling point count during manual/mechanicalcompression, and

$\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}$represents an accumulated sampling point count within a CPR interruptionperiod present in the manual/mechanical compression process (p=1, 2, 3,. . . P, and q=1, 2, 3, . . . Q, where p represents a p^(th) CPRinterruption period, P represents a total number of CPR interruptionperiods present in the manual/mechanical compression process having alength of N points, q represents a q^(th) point during the p^(th) CPRinterruption period, and Q represents a total point count of the p^(th)CPR interruption period).

As described above, the sampling rate may have corresponding relationwith respect to the time. When calculating the Interval_(Ratio) ^(CPR),the

$\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}$and the

$\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}$related to the sampling rate should be transformed into time scale.Since the two may have the same sampling rate, the factor for samplingrate transformation can be eliminated from the calculation formula ofthe Interval_(Ratio) ^(CPR). As a result, the Interval_(Ratio) ^(CPR) issubstantially equivalent to the percentage in the time scale and it canreflect the ratio between the CPR interruption period and the totalmanual/mechanical compression period.

In clinical applications, the Interval_(Ratio) ^(CPR) can be updateddynamically in real time. That is, once the blood oxygen system acquiresa sampling point during the rescue process by manual/mechanicalcompression, the acquired sampling point may be counted to update the

${\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}},$whether the acquired sampling point is obtained during the CPRcompression interruption period can be evaluated based on theabove-described evaluation method, and the

$\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}$can then be updated following the evaluation result. Correspondingly,the total time percentage Interval_(Ratio) ^(CPR) can be updated everyone sampling point. In this embodiment, the Interval_(Ratio) ^(CPR) canbe updated according to the sampling rate (i.e., it can be updated everyone second). In FIG. 23, “CPR Interval Ratio” shows that theInterval_(Ratio) ^(CPR) be present on the display interface as startingthe manual/mechanical compression.

As described above, about three pulse waves may be needed forrecognition, so as to evaluate whether the current state is thecontinuous compression state or the compression interruption state. TheInterval_(Ratio) ^(CPR) may thus be displayed with a certain time delay,where for example, the Interval_(Ratio) ^(CPR) FIG. 23 is actuallydisplayed at the position 4 rather than the in theoretical position 3.Typically, the delay time can be set as about 1.64 s.

The total time percentage of the CPR compression interruption period maybe continuously displayed during the whole manual/mechanical compressionprocess until the manual/mechanical compression state is reset. In thisregard, two methods may be used to reset the total time percentage ofthe CPR compression interruption period. That is, the total timepercentage of the CPR compression interruption period may be reset whenthe restoration of spontaneous circulation is recognized during themanual/mechanical compression process and/or when a reset mechanism istriggered by manual operation (e.g., clicking on a reset button of amonitoring apparatus).

In step 214, the counting information can be outputted. For example, thecounting information such as the duration of the disappearing period ofthe pulse wave and/or the total time percentage of the disappearingperiod of the pulse wave can be outputted and displayed on a displayscreen.

Steps 102-108 and 202-210 are related to the feature evaluation based onthe pulse wave recognition in the time domain. Due to energyconservation between the time domain and the frequency domain, suchfeature evaluation on the pulse wave can also be implemented by afrequency-domain method. The frequency-domain analysis method may dependon the data length. In the event of too large data, the variationtendency of the physiological signals may become too slow; when the datalength is too short, the data accuracy may not be high enough to causeinvalid frequency-domain analysis. In this disclosure, the data lengthfor each frequency-domain analysis can be set as about 6 seconds incombination of clinical application. In order to follow the variationsof the physiological signal rapidly, the frequency-domain analysis maybe started every 0.5 seconds.

The width characteristic and the amplitude characteristic of the pulsewave in the time domain may be mapped into signal amplitude and signalwidth in the frequency domain. Therefore, an amplitude parameter or anarea parameter of a frequency peak can be used to evaluate thedisappearing duration and the total time percentage of the disappearingduration during the manual/mechanical compression process. When the CPRcompression interruption period is recognized, the frequency-domainanalysis may be started every 0.5 seconds, and the amplitude or the areaof the frequency peak may decrease gradually. An amplitude threshold oran area threshold can be established, and the current compression statecan be deemed to be the manual/mechanical compression interruptionperiod when none of the amplitude values or the area values of one ormore frequency peak (e.g., about four) is higher than the correspondingthreshold.

The duration of the manual/mechanical compression interruption periodmay also be displayed after a certain time delay, where the delay timemay depend on an interval and the number of the respectivefrequency-domain analysis. As mentioned above, since the interval of therespective frequency-domain analysis may be about 0.5 seconds and thefrequency-domain analysis may be performed for four times, the delaytime in the frequency domain can be approximately 2 seconds. Here, aminimum resolution of the CPR interruption period may be constrained bythe interval of the frequency-domain analysis to be about 0.5 seconds,for example. When the manual/mechanical compression interruption stateis recognized, the time counting & displaying operations can be startedfor the manual/mechanical compression interruption period; when themanual/mechanical continuous compression state is recognized, the timecounting operation for the manual/mechanical compression interruptionperiod can be shut down. During the frequency-domain analysis, the totaltime percentage of the manual/mechanical compression interruption period(i.e., the total time percentage of the CPR compression interruptionperiod) may be calculated once starting the manual/mechanicalcompression. By performing the frequency-domain analysis every 0.5seconds, a total duration (i.e., the CPR duration) may be accumulated, acurrent state is the CPR compression interruption period can beevaluated, and the duration of the CPR compression interruption periodcan be accumulated. Here, the total time percentage of the CPRcompression interruption period may refer to a ratio between theduration of the CPR compression interruption period and the CPRduration, and a minimum resolution of the total time percentage of theCPR compression interruption period may be constrained by the intervalof the frequency-domain analysis. The starting and reset mechanisms inthe frequency domain can be the same as those in the time domain.

Based on the above-described methods, the embodiments of this disclosuredescribe CPR quality feedback systems. As shown in FIG. 12, an exampleCPR quality feedback system may include a data acquisition unit 40, awaveform generation unit 41, a calculation unit for peripheralcirculation parameter related to CPR quality 42 and a feedback unit 43.The data acquisition unit 40 can be used to acquire the blood oxygensignals of the test subject undergoing CPR. The waveform generation unit41 can be used to generate a pulse oximetry waveform based on theacquired blood oxygen signals. The calculation unit for peripheralcirculation parameter related to CPR quality 42 can be used to calculateperipheral circulation parameters related to CPR quality based on thepulse oximetry waveform. The feedback unit 43 can be used to providefeedback on the peripheral circulation parameter related to CPR quality.The peripheral circulation parameters related to CPR quality may includethe blood oxygen characteristic of the pulse oximetry waveform and theperipheral circulation parameters generated by compression. Theperipheral circulation parameters generated by compression may includethe amplitude characteristic of a single pulse wave and/or the areacharacteristic of a single pulse wave. When providing feedback on theCPR implementation quality, the blood oxygen characteristic and theamplitude characteristic of a single pulse wave can be used to evaluatefor CPR quality. The blood oxygen characteristic and the areacharacteristic of a single pulse wave can also be used to evaluate theCPR implementation quality. Further, the blood oxygen characteristictogether with the amplitude characteristic and the area characteristicof a single pulse wave can be used to evaluate the CPR quality. In thisembodiment, the last situation using the blood oxygen characteristic aswell as the amplitude characteristic and the area characteristic ofsingle pulse wave is described in more detail. In the evaluationprocess, the amplitude characteristic of single pulse wave may be anabsolute amplitude value or an amplitude index; the amplitude index is aratio between the absolute amplitude value of a single pulse wave of thefluctuant component of amplified/reduced pulse oximetry waveform and thecorresponding DC component. The area characteristic of a single pulsewave may be an absolute area value or an area index; the area index is aratio between the absolute area value of a single pulse wave of thefluctuant component of amplified/reduced pulse oximetry waveform and thecorresponding DC component.

Since the original pulse oximetry waveform may contain the constantcomponent and the fluctuant component, the calculation unit forperipheral circulation parameters related to CPR quality 42 can firstseparate out the constant component and the fluctuant component from thepulse oximetry waveform, then calculate the peripheral circulationparameters generated by the compression based on the fluctuant componentof the pulse oximetry waveform, and then calculate the blood oxygenfrequency characteristic based on the pulse oximetry waveform or basedon the fluctuant component of the pulse oximetry waveform.

In an embodiment, the feedback unit 43 may convert the peripheralcirculation parameter related to CPR quality into video information thatcan be displayed on a display interface, so that parameters (forexample: the blood oxygen characteristic, the amplitude characteristicof single pulse wave, and the area characteristic of single pulse wave)appear on the display interface.

In another embodiment, the feedback unit 43 may convert the peripheralcirculation parameters generated by compression (such as the amplitudecharacteristic and the area characteristic of a single pulse wave) intowaveform data that can be displayed on a display interface, so as tofacilitate the user to observe the variations of the amplitudecharacteristic and the area characteristic.

Theoretically, the amplitude characteristic should exhibit linearcorrelation with the compression depth. When the compression depth isstable, the parameter value of the amplitude characteristic should bestable with less fluctuations. In a clinical CPR process, thecompression may be unstable at the beginning stage, in which case theindex value of the amplitude characteristic are unstable withsignificant fluctuations. With the stabilization of the compressiondepth, the index values of the amplitude characteristic can becomerelatively stable. The area characteristic may exhibit linear positivecorrelation with the cardiac ejection volume in every compression. Whenthe compression depth is stable and the compression frequency isconstant, the parameter values of the area characteristic should bestable with less fluctuations. In a clinical CPR process, thecompression depth and the compression frequency may be unstable at thebeginning stage, in which case the outputted index values of the areacharacteristic may also be unstable with significant fluctuations,namely the change range of values is relatively wide. With thestabilization of the compression depth and the compression frequency,the index values of the area characteristic can become relatively stable(i.e., the value variations may be concentrated within a small range offluctuations). Therefore, the user may evaluate whether the compressiondepth and the compression frequency are stable by observing thevariations of the amplitude characteristic and the area characteristic.

In clinical practice, the compression depth should be greater than orequal to about 5 cm. The amplitude characteristic can directly reflectthe compression depth. In such case, if the user can find the mappingvalue corresponding to the compression depth of about 5 cm and displaythis value on the waveform graph of the amplitude characteristic, theuser can conveniently evaluate whether the compression depth has met theguideline recommendations according to the value of the displayedamplitude characteristic. The corresponding relation between thedisplayed amplitude characteristic and the compression amplitude can beestablished according to a series of tests on animal and/or humanbodies, and then mapping the value of the amplitude characteristic whenthe compression depth is at least about 5 cm. This mapping value mayconstitute the amplitude distribution range limit related to thestandard or determined limit value of cardiac compression depth, whichcan be displayed on the same interface with the amplitude waveform data.When the amplitude characteristic has reached this mapping value withminimal fluctuations, it may be concluded that the compression depth hasreached the guideline standard or determined limit. In this embodiment,the compression depth of at least 5 cm is taken as an the referencestandard, although this can be modified according to the data onpractical clinical applications.

In the case of the waveform graph of the area characteristic, the areadistribution range limit related to the standard value of cardiaccompression depth and the area waveform data can be displayed on thesame waveform graph of the area characteristic. When the areacharacteristic falls within the area distribution range limit, it may beconcluded that the compression depth and the compression frequency havebasically reached the standard or determined limit.

When evaluating CPR quality, the user may observe the waveform graphs ofthe amplitude characteristic and the area characteristic. In anotherembodiment, feedback and control on the CPR implementation quality canalso be made by automatic evaluation and prompt adjustments. As shown inFIG. 13, the CPR quality feedback system in this embodiment may includea data acquisition unit 40, a waveform generation unit 41, a calculationunit for peripheral circulation parameter related to CPR quality 42, afeedback unit 43, a first prompt unit 44, a second prompt unit 45 and acontrol module 46. The data acquisition unit 40, the waveform generationunit 41, the calculation unit for peripheral circulation parameterrelated to CPR quality 42 and the feedback unit 43 can be the same asthose in the embodiment as shown in FIG. 12. The first prompt unit 44can be used to calculate the fluctuating value of the amplitudecharacteristic and evaluate whether the fluctuating value of theamplitude characteristic is less than a first preset value and whetherthe amplitude characteristic falls within the amplitude distributionrange limit. If so, the system may output a first prompt message, wherethe first prompt message can be used to inform the user that the presentcompression depth has reached the standard or determined limit. Thefirst prompt unit 44 can output a first result information when thefluctuating value of the amplitude characteristic is less than the firstpreset value but the amplitude characteristic does not fall within theamplitude distribution range limit. The second prompt unit 45 can beused to calculate the fluctuating value of the area characteristic andevaluate whether the fluctuating value of the area characteristic isless than a second preset value and whether the area characteristicfalls within the area distribution range limit. If so, the second promptunit 45 may output a second prompt message, where the second promptmessage can be used to inform the user that the present compressionquality has reached the guideline standard or determined limit. Thesecond prompt unit 45 can output a second result information when thefluctuating value of the area characteristic is less than the secondpreset value, but the area characteristic does not fall within the areadistribution range limit. The second prompt unit 45 can also output athird result information when the area characteristic falls within thearea distribution range limit and the fluctuating value of the areacharacteristic is less than the second preset value. The control module46 can be used to command a CPR instrument 47 to increase thecompression depth when the control module 46 has received the firstresult information, the second result information and the third resultinformation. After the CPR instrument 47 increases the compression depthaccording to the third result information, the control module 46 cannotify the calculation unit for peripheral circulation parameter relatedto CPR quality 42 to calculate the area characteristic of a single pulsewave, and evaluate whether the calculated area characteristic ismaximal. If not, the calculation unit 42 may output a fourth resultinformation to the control module 46, based on which the control module46 can command the CPR instrument 47 to appropriately increase thecompression depth. Otherwise, the calculation unit 42 may output a fifthresult information and a third prompt message, based on which thecontrol module 46 can control the CPR instrument 47 to maintain thecurrent compression depth. The third prompt message can be used toinform the user that the test subject has reached an optimal compressionstate.

In this embodiment, the data acquisition unit 40, the waveformgeneration unit 41, the calculation unit for peripheral circulationparameter based on pulse oximeter 42, the feedback unit 43, the firstprompt unit 44, the second prompt unit 45 and the control module 46 canbe integrated into one module or can be separately integrated intomultiple modules.

Based on the above-described methods and/or systems, the embodiments ofthis disclosure can provide medical devices. As shown in FIG. 14, anexample medical device can include a blood oxygen probe 51, a bloodoxygen module 52 and an output module 53. Herein the blood oxygen probe51 can be used to probe a measured position of a test subject and detectblood oxygen signals of the test subject in real time. The blood oxygenmodule 52 coupled with the blood oxygen probe 51 can be used to acquirethe blood oxygen signals outputted by the blood oxygen probe 51,generate a pulse oximetry waveform based on the blood oxygen signals,calculate peripheral circulation parameters related to CPR quality basedon the pulse oximetry waveform, and output relevant information of suchparameters. The output module 53 coupled to the blood oxygen module 52can be used to provide feedback on the relevant information on theparameters outputted by the blood oxygen module 52.

Any suitable probe can be used as the blood oxygen probe 51 as long assuch probe can detect the blood oxygen signals. As shown in FIG. 2, theblood oxygen probe 51 can include a light-emitting device 100 and aphotoelectric detector 101, which may be oppositely disposed on bothsides of the blood oxygen probe 51. To calculate the blood oxygensaturation, the light-emitting device 100 may include a redlight-emitting tube and an infrared light-emitting tube. In the processof detection, the light emitted by the light-emitting device 100 maypenetrate through the arterial blood vessel at the detection positionand reach the photoelectric detector 101, and the photoelectric detector101 can be used to convert the detected red light or infrared light thathas penetrated through the arterial blood vessel to electrical signalsand output such electrical signals. When the detected blood oxygensignals are used to evaluate for CPR quality, the signals of red lightor infrared light may be used to acquire a waveform. Therefore, thelight-emitting device 100 may only include a red light emitting tube oran infrared light emitting tube.

In some embodiments, the blood oxygen module 52 and the blood oxygenprobe 51 can be connected through a probe accessory 54, where the probeaccessory 54 may be a connecting wire. In some embodiments, the bloodoxygen module 52 and the blood oxygen probe 51 can realize a signalconnection through wireless communication. For example, wirelesscommunication modules can be respectively mounted on the blood oxygenprobe 51 and the blood oxygen module 52.

The blood oxygen module 52 can be used to acquire the blood oxygensignals outputted by the blood oxygen probe 51, generate the pulseoximetry waveform based on the blood oxygen signals, and calculate theperipheral circulation parameters related to CPR quality based on thepulse oximetry waveform by using the above-described methods and/orsystems. The peripheral circulation parameters related to CPR qualitycan include the blood oxygen frequency characteristic of the pulseoximetry waveform and the peripheral circulation parameters generated bycompression. The peripheral circulation parameters generated bycompression can include the amplitude characteristic of a single pulsewave and/or the area characteristic of a single pulse wave. Theamplitude characteristic of a single pulse wave can be an absoluteamplitude value or an amplitude index, while the area characteristic ofa single pulse wave can be an absolute area value or an area index.

In the embodiments of this disclosure, the output module 53 can be usedto output various associated information reflecting the peripheralcirculation relevant parameters. The associated information may includebut is not limited to video information, audio information and lightinformation. The video information can include but is not limited to thetrend chart reflecting the dynamic variations of the peripheralcirculation relevant parameters, the target range information of theperipheral circulation relevant parameters related to the standard CPRquality, the first alarm message when the peripheral circulationrelevant parameters exceed their target range, as well as the secondwarning information when the dynamic variations of the peripheralcirculation relevant parameters exceed their acceptable range ofvariation. The audio information mainly refers to the auditory sensebased on sound variation, including but not limited to parameter valueinformation, parameter variation tendency information, warning promptmessage, current compression quality and compression adjustment prompt.These data can be conveyed through either/both a lighted prompt or anaudible sound playing the function of a prompt. The light informationherein refers to the visual sense based on light variation. It can be aflashing light when the peripheral circulation parameter informationexceeds the target range or the stability is too low. It can also beindicated using lamps of different colors to indicate the currentcompression quality by color change.

In an embodiment, the output module 53 can be designed as a soundplaying module. When the data outputted by the blood oxygen module 52 isthe audio information related to the peripheral circulation parametersrelated to CPR quality, the sound playing module can output this dataaudibly. For example, the output module 53 can notify the user of thecurrent compression state in the form of sound.

In an embodiment, the output module 53 can also be a display module.When the data outputted by the blood oxygen module 52 is the videoinformation related to the peripheral circulation parameters related toCPR quality, the display module can display the video informationrelated to these parameters in visual mode on the display interface. Thevideo information can be displayed in the form of text or image, such aswaveform graph.

In an embodiment, the blood oxygen module 52 can separate out theconstant component and the fluctuant component from the pulse oximetrywaveform, calculate the amplitude characteristic and the areacharacteristic of a single pulse wave based on the fluctuant componentof the pulse oximetry waveform, and calculate the blood oxygencharacteristic based on the pulse oximetry waveform or based on thefluctuant component of the pulse oximetry waveform. The blood oxygencharacteristic, the amplitude characteristic, the area characteristic aswell as some associated data can be processed into video information andfurther outputted to the display module, where the blood oxygencharacteristic may be displayed in the mode of text in real time, theamplitude characteristic and the area characteristic displayed in themode of waveform graph in real time, while the amplitude distributionrange limit and the area distribution range limit (related to thestandard values of cardiac compression depth) respectively displayed onthe waveform graphs of the amplitude characteristic and the areacharacteristic. The user may evaluate whether the compression qualityhas reached the standard by observing the values of the blood oxygencharacteristic, the amplitude characteristic and the area characteristicdisplayed in real time as well as the fluctuation conditions of theamplitude characteristic and the area characteristic. The blood oxygenmodule 52 can also be used to respectively calculate the fluctuatingvalues of the amplitude characteristic and the area characteristic. Whenthe fluctuating value is less than the preset threshold, the system mayoutput the corresponding prompt message so that the evaluation resultcan be more accurate and visual.

In an embodiment, the blood oxygen module 52 can operate to recognizethe fluctuant components and the constant components in the acquiredblood oxygen signals and generate the pulse waveform based on theseparated fluctuant components. In an embodiment, the blood oxygenmodule 52 may also operate to calculate/count the duration of adisappearing period of the pulse wave and/or a total time percentage ofthe disappearing period of the pulse wave. The total time percentage ofthe disappearing period of the pulse wave may refer to a ratio betweenthe accumulated duration of the disappearing period of the pulse waveand the duration of the CPR operation. In an embodiment, the bloodoxygen module 52 may further operate to calculate/count the duration ofan appearing period of the pulse wave and/or a total time percentage ofthe appearing period of the pulse wave. Here, the appearing period ofthe pulse wave refers to a duration in which the pulse wave can begenerated and/or detected. Alternatively, such an appearing period canbe determined by subtracting the disappearing duration from the CPRduration.

In an embodiment, the blood oxygen module 52 may also preset a firstthreshold and a second threshold, and prompt warning information whenthe disappearing duration exceeds the first threshold and/or when thetotal time percentage exceeds the second threshold.

In an embodiment, the blood oxygen module 52 can calculate the totaltime percentage of the disappearing period of the pulse wave by thefollowing formula:

$\begin{matrix}{{Interval}_{Ratio}^{CPR} = {\frac{\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}}{\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}}*100\%}} & (15)\end{matrix}$

where

$\sum\limits_{n = 1}^{N}{{CPR}_{course}(n)}$represents an accumulated sampling point count during manual/mechanicalcompression, and

$\sum\limits_{p = 1}^{P}{\sum\limits_{q = 1}^{Q}{{Interval}\left( {p,q} \right)}}$represents an accumulated sampling point count within amanual/mechanical compression interruption period present in themanual/mechanical compression process (p=1, 2, 3, . . . P, and q=1, 2,3, . . . Q, where p represents a p^(th) manual/mechanical compressioninterruption period, P represents a total number of themanual/mechanical compression interruption periods present in themanual/mechanical compression process having a length of N points, qrepresents a q^(th) point during the p^(th) CPR interruption period, andQ represents a total point count of the p^(th) manual/mechanicalcompression interruption period).

In an embodiment, the blood oxygen module 52 can calculate the totaltime percentage of compression duration (Compression_(Ratio) ^(CPR)) by:1−Interval_(Ratio) ^(CPR).

In an embodiment, the blood oxygen module 52 can use a plurality ofsingle pulse waves to recognize the disappearing period based on thevariations of the multiple pulse waves. In an embodiment, the bloodoxygen module 52 can extract about three continuous single pulse wavesand recognize the disappearing period of the pulse wave based on an areavariation and a shape variation of the multiple single pulse waves.

In addition to providing feedback on the CPR quality by using theperipheral circulation parameters related to CPR quality, the medicaldevice described herein can also be connected with another medicaldevice so as to improve the accuracy of the interaction between thatanother medical device and the test subject. In such case, the medicaldevice can also include an interaction control interface to make datacommunication with the other medical device. Through this interactioncontrol interface, the user may further control the automaticswitch-over of the functional modes of that another medical device.Specifically, the blood oxygen module 52 can evaluate the current CPRquality according to whether the calculated parameter values of theperipheral circulation parameters are reaching the preset standard andwhether the fluctuating values are exceeding the corresponding presetvalue. It can then further adjust the configuration and the output ofthat another medical device according to the evaluation result. Theadjusted configuration and output can include but are not limited tocompression time phase, compression depth (force) and compressionfrequency performed on the test subject. The adjusted configuration andoutput can also include keeping the current compression state andincreasing the compression depth (force). The fact that theseconfigurations adjust according to the peripheral circulation parametersrelated to CPR quality may enable the other medical device to performmore accurately on the test subject.

In an embodiment, the interaction control interface can make theconnected medical device, and the interaction control interface can be aCPR instrument interface. When the CPR instrument is connected, the CPRinstrument may be properly controlled according to the feedbackcondition so that the CPR instrument can operate at an acceptable statefor the resuscitation of the test subject. The detailed description onthe control method will be given as follows.

(See FIG. 14) The medical device may also include a control module 55and a CPR instrument interface 56, where the control module 55 canrespectively have a signal connection with the CPR instrument interface56 and the blood oxygen module 52. When the CPR instrument is designedfor automatic regulation of the compression state, the CPR instrumentcan be connected through the CPR instrument interface 56, and thecontrol module 55 can communicate with the CPR instrument through theCPR instrument interface 56. For example, the control module 55 canreceive the information transmitted from the CPR instrument and controlthe compression frequency and the compression depth of the CPRinstrument according to an initial default setting or the feedbackinformation from the blood oxygen module 52.

At the beginning of CPR, the control module 55 can notify the CPRinstrument to start operation according to the default compressionfrequency and compression depth. While the CPR instrument is working,the blood oxygen probe 51 can be used to detect the blood oxygen signalsof the test subject, and the blood oxygen module 52 can be used tocalculate the blood oxygen characteristic, the amplitude characteristic,and the area characteristic of a single pulse wave based on the bloodoxygen signals. In this process, the blood oxygen module 52 may furtheroperate to calculate the fluctuating values of the amplitudecharacteristic and the area characteristic, evaluate whether thefluctuating value of the amplitude characteristic is less than the firstpreset value and whether the amplitude characteristic falls within theamplitude distribution range limit, and evaluate whether the fluctuatingvalue of the area characteristic is less than the second preset valueand whether the area characteristic falls within the area distributionrange limit. If the fluctuating value of the amplitude characteristic isless than the first preset value but the amplitude characteristic doesnot fall within the amplitude distribution range limit, the blood oxygenmodule 52 may output the first result information to the control module55, and then the control module 55 can command the CPR instrument toincrease the compression depth according to the first resultinformation. If the fluctuating value of the area characteristic is lessthan the second preset value but the area characteristic does not fallwithin the area distribution range limit, the blood oxygen module 52 mayoutput the second result information to the control module 55, and thecontrol module 55 can, according to the second result information,control the CPR instrument to increase the compression depth. If thearea characteristic falls within the distribution range limit and thefluctuating value of the area characteristic is less than the secondpreset value, the blood oxygen module 52 may output the third resultinformation to the control module 55, and the control module 55 cancontrol the CPR instrument to increase the compression depth accordingto the third result information. The information of increasing thecompression depth can then be provided to the blood oxygen module 52,which may calculate the area characteristic of a single pulse wave afterincreasing the compression depth, and, based on this feedback, evaluatewhether the area characteristic of single pulse wave after increasingthe compression depth is at its maximal value. If not, the system mayoutput the fourth result information; otherwise, the system can outputthe fifth result information. The control module 55 can notify the CPRinstrument to increase the compression depth according to the fourthresult information, or control the CPR instrument to maintain thecurrent compression depth according to the fifth result information.

In clinical applications, the medical device can be a typical bedsideequipment such as a patient monitor, defibrillator andelectrocardiograph. A blood oxygen module can be added onto the existingbedside equipment. The blood oxygen module can be an independent moduleor a circuit integrated into the bedside equipment. The functions of theblood oxygen module can be realized by any of the afore-describedmethods and/or systems through a computer executable program. Thedisplay module of the bedside equipment can be used as the outputmodule, and the host of the bedside equipment can be used as the controlmodule, or the control module can be integrated into the host of thebedside equipment.

This embodiment discloses a pulse oximeter plug-in that can be used incoordination with the bedside equipment to give real-time feedback ofCPR implementation quality. As shown in FIG. 15, the pulse oximeterplug-in can include an enclosure 61, a blood oxygen signal interface 62,a blood oxygen module (not shown in this figure) and an output interface(not shown in this figure). The enclosure 61 may have a user orientedpanel 611 and a back panel 612 in contact with the host. The bloodoxygen signal interface 62 may be positioned on the panel 611 of theenclosure 61 and used to connect with accessory/device 64 of the bloodoxygen probe. The output interface can be positioned on the back panel612 of the enclosure and used to contact with a corresponding interface631 on the host. In an embodiment, the output interface can be aconductive contact or a plug port. The blood oxygen module may belocated in the enclosure 61. The blood oxygen module can be connected tothe blood oxygen signal interface 62 and the output interface, and maycommunicate with the host through the output interface. The blood oxygenmodule can be used to receive the blood oxygen signals from the bloodoxygen signal interface 62, generate the pulse oximetry waveform basedon the blood oxygen signals, calculate the peripheral circulationparameters related to CPR quality based on the pulse oximetry waveform,and output the relevant information of the parameters. The host 63 ispositioned in the bedside equipment. In any of the above-describedmethods and/or systems, the blood oxygen module can process the bloodoxygen data and transmit the data to the host, and then the host maydisplay the data through the display module of the bedside equipment forpresenting of the CPR implementation quality to the user.

In an embodiment, the relevant information outputted by the blood oxygenmodule on the peripheral circulation parameters related to CPR qualitymay include video information, where the video information can includethe waveform data of the amplitude characteristic or the waveform dataof the area characteristic. The waveform data of the amplitudecharacteristic may include the amplitude distribution range limitrelated to the standard value of cardiac compression depth, and thewaveform data of the area characteristic may include the areadistribution range limit related to the standard value of cardiaccompression depth. The blood oxygen module can also be used to calculatethe fluctuating value of the amplitude characteristic, and evaluatewhether the fluctuating value of the amplitude characteristic is lessthan the first preset value and whether the amplitude characteristicfalls within the amplitude distribution range limit. If so, the systemmay output the first prompt message, where the first prompt message canbe used to inform the user that the current compression depth hasreached the standard or determined limit. If the blood oxygen moduleevaluates that the fluctuating value of the amplitude characteristic isless than the first preset value but the amplitude characteristic doesnot fall within the amplitude distribution range limit, the system mayoutput the first result information, where the first result informationcan be used to command the CPR instrument to increase the compressiondepth. The blood oxygen module can also be used to calculate thefluctuating value of the area characteristic, evaluate whether thefluctuating value of the area characteristic is less than the secondpreset value and whether the area characteristic falls within the areadistribution range limit. If so, the system may output the second promptmessage, where the second prompt message can be used to inform the userthat the current compression quality has reached the standard. If theblood oxygen module evaluates that the fluctuating value of the areacharacteristic is less than the second preset value but the areacharacteristic does not fall within the area distribution range limit,the system may output the second result information, which can be usedto command the CPR instrument to increase the compression depth.

In an embodiment, the blood oxygen module/device/accessory 64 can havethe structure as shown in FIG. 16 and include a sampling circuit 641, adata processing circuit 642 and a receiving-transmitting circuit 643.The sampling circuit 641 can be coupled to the blood oxygen signalinterface 62 and be used to take samples of the blood oxygen signalsinputted by the blood oxygen signal interface 62. The data processingcircuit 642 may function as the blood oxygen module and can be coupledto the output-end of the sampling circuit 641. The data processingcircuit 642 may be used to generate the pulse oximetry waveform based onthe sampled blood oxygen signals, calculate the peripheral circulationparameters related to the CPR quality based on the pulse oximetrywaveform, and output the information related to these parameters afterdata processing. In this embodiment, the data processing circuit 642 canbe a microprocessor MCU, and its functions can be realized by a computerexecutable program. The receiving-transmitting circuit 643 can beconnected between the data processing circuit 642 and the outputinterface, and used to achieve the communication between the dataprocessing circuit 642 and the host 63 through the output interface. Theblood oxygen module 64 may also include some peripheral circuits, suchas the amplifying circuit to amplify the sampled signals and/or thefiltering circuit to filter the sampled signals. The peripheral circuitsmay also include a voltage stabilizing circuit, where the voltagestabilizing circuit can be used to receive power from the host throughthe output interface and then provide electric power for each part ofthe circuits after voltage regulation.

In an embodiment, the pulse oximeter plug-in can realize wirelesscommunication with the host. For example, the receiving-transmittingcircuit 643 may include a wireless communication module, and the hostmay also include a wireless communication module, so that thecommunication between the pulse oximeter plug-in and the host can bewirelessly achieved. In this embodiment, the pulse oximeter plug-in hasno need for the output interface, and it has no need to directly contactthe host either, which means it can be placed apart from the host.

In an embodiment, a medical equipment may include an opticaltransceiver, a digital processor and an output module. The opticaltransceiver can include a light emitting tube and a receiving tube,where the light emitting tube can emit at least one light signal topenetrate through human tissue, and the receiving tube can receive theat least one light signal and convert the at least one light signal intoat least one electrical signal. The digital processor can convert the atleast one electrical signal into at least one digital signal and processthe at least one digital signal to obtain peripheral circulationrelevant parameters. Based on the signal processing, the digitalprocessor can further recognize a pulse wave and count duration of adisappearing period of the pulse wave. The output module can outputassociated information corresponding to the peripheral circulationrelevant parameters and the counting information.

In an embodiment, the digital processor can recognize the pulse wave byrecognizing real-time pulsatile perfusion characteristic reflected bythe digital signal. In an embodiment, the digital processor can obtainthe real-time pulsatile perfusion characteristic reflected by thedigital signal by identifying fluctuant components and constantcomponents in the at least one digital signal.

In an embodiment, the counting information may include the disappearingduration of the pulse wave. In another embodiment, the countinginformation may also include the appearing duration of the pulse wave,i.e. the continuous compression period during CPR operation. The outputmodule can be a display interface, and the disappearing duration of thepulse wave can be displayed on the display interface. In anotherembodiment, the counting information may also include a total timepercentage of the disappearing period of the pulse wave, which may referto a ratio between an accumulated duration of the disappearing period ofthe pulse wave and duration of the CPR operation. The display interfacemay also display the total time percentage of the disappearing period ofthe pulse wave. The digital processor may also preset a first thresholdand a second threshold, and prompt warning information when thedisappearing duration exceeds the first threshold and/or when the totaltime percentage exceeds the second threshold.

In a case of cardiac arrest for any patient in or outside a hospital,medical staff can immediately connect the patient to a monitor duringemergency treatment, so as to display the heart rate, blood pressure,respiration and pulse oximeter saturation of the patient. For thepatient in cardiac arrest, an effective first aid method is high-qualityCPR of which a factor is high-quality chest compression. Clinically, theparameters for evaluating the compression quality may includecompression position, compression frequency, compression depth,compression-relaxation time proportion and thorax rebound condition. Inthe case of incorrect compression position, insufficient depth, toohigh/low frequency and/or insufficient relaxation, the CPR quality canbe affected. The embodiments of this disclosure may find such variationand the provide feedback to the medical staff regarding the CPRimplementation quality in real-time by using the peripheral circulationparameters calculated based on a pulse oximetry waveform. Furthermore,the systems are also non-invasive to the patient. When the systems areused in coordination with an automatic resuscitator, the control on theautomatic resuscitator can be realized according to the feedbackinformation. In emergency treatment, the blood oxygen saturation of thepatient is often detected to measure the blood oxygen signals of thepatient. Therefore, the embodiments of this disclosure generally have noneed for additional feedback device, thus being convenient andeconomical in practice.

The following test results describe the peripheral circulationparameters related to CPR quality that can be calculated according tovarious embodiments described herein and used for evaluation of CPRimplementation quality.

In animal experiment, the automatic resuscitator is used for chestcompression. Two indexes, compression frequency and compressionposition, are selected herein. According to the compression depth, theCPR implementation quality is divided into high quality (5 cm), mediumquality (4 cm) and low quality (3 m). In these three cases, the systemoutputs the value, the waveform, the amplitude and the area under thecurve of pulse oximeter saturation, where the amplitude and the areaunder the curve include the real-time value and the average value in 30seconds. The average values with higher reference value are used toreduce error as shown in FIGS. 17-21. As shown in FIG. 17, when thepatient has spontaneous circulation, the value of the pulse oximetersaturation is high while the values of the amplitude and the area underthe curve are also high. As shown in FIG. 18, when the spontaneouscirculation of the patient has disappeared (in case of cardiac arrest),the value of the pulse oximeter saturation cannot be measured, and thevalues of the amplitude and the area under the curve are displayed aszero or extremely low values. In case of low-quality CPR, the values ofsuch parameters are relatively lower as shown in FIG. 19. In case ofmedium quality CPR, the values of the amplitude and the area under thecurve are higher than those of low-quality CPR as shown in FIG. 20. Incase of high-quality CPR, the values of various parameters are higher asshown in FIG. 21.

In practice, if the relevant parameter values outputted in real time arelower than the specified values of high-quality CPR, the resuscitationquality should be enhanced to realize high-quality resuscitation,improve the vital organ perfusion and overall prognosis. The CPRmonitoring feedback systems described herein can reflect CPR quality ina real-time, convenient, non-invasive and economical manner, and thuscan be widely used and applied to the field of cardio-pulmonaryresuscitation. For clinicians, this disclosure can provide visual andreal-time monitoring feedback indexes to improve CPR quality. Therefore,this disclosure has great practical application value and broadapplication prospects. Furthermore, it has high social value for thedevelopment of health care industry and for improving outcomes inresuscitation for the people.

Those skilled in the art can understand that, all or partial steps ofvarious methods in the embodiments above can be completed by using aprogram to command relevant hardware products. This program can bestored in a readable storage medium of the computer, and the storagemedium may include ROM, RAM, disk or optical disk.

The above content gives further detailed descriptions on this disclosurein combination with specific embodiments. Specific implementations ofthis disclosure are not limited to these descriptions. For those skilledin the art, various substitutions can be made without deviation from theconcept and spirit of this disclosure.

The invention claimed is:
 1. A cardio-pulmonary resuscitation (CPR)monitoring device, comprising: an optical transceiver comprising: alight emitting tube that emits at least one light signal; and areceiving tube located with respect to the light emitting tube toreceive the at least one light signal after the at least one lightsignal has passed through human tissue as at least one transmissionsignal through the human tissue and convert the at least one lightsignal into at least one electrical signal; a digital processor toconvert the at least one electrical signal into at least one digitalsignal reflecting at least one peripheral circulation parameter relatedto CPR quality; wherein the digital processor obtains the at least oneperipheral circulation parameter by separating a fluctuant component anda constant component of the at least one digital signal, and wherein theCPR quality is related to at least one of an absolute amplitude value oran absolute area value of at least one single pulse wave in theseparated fluctuant component, wherein each single pulse wave ismeasured from a wave trough to an adjacent wave crest, wherein thedigital processor processes the at least one digital signal using afrequency domain analysis method; and an output module to outputinformation corresponding to the at least one peripheral circulationparameter related to CPR quality.
 2. The CPR monitoring device of claim1, wherein the at least one peripheral circulation parameter reflects adepth variation characteristic of CPR compression.
 3. The CPR monitoringdevice of claim 2, the digital processor obtains the at least oneperipheral circulation parameter by identifying a fluctuant component ofthe at least one digital signal and making an amplitude conversion onthe fluctuant component.
 4. The CPR monitoring device of claim 1,wherein the at least one peripheral circulation parameter reflects anarea variation characteristic of CPR compression.
 5. The CPR monitoringdevice of claim 4, the digital processor obtains the at least oneperipheral circulation parameter by identifying a fluctuant component ofthe at least one digital signal and making an area conversion on thefluctuant component.
 6. The CPR monitoring device of claim 1, whereinthe frequency domain analysis method is used for frequency spectrumidentification based on a non-zero frequency spectrum.
 7. The CPRmonitoring device of claim 1, wherein the frequency domain analysismethod is used for frequency spectrum identification based on a ratiobetween a non-zero frequency spectrum and a zero-frequency spectrum. 8.The CPR monitoring device of claim 1, wherein the CPR monitoring deviceis configured as a medical device plug-in, the medical device plug-incomprising: an enclosure component; a physiological signal acquisitioninterface positioned on an external surface of the enclosure componentfor connection with signal acquisition accessories; a physiologicalsignal processing module positioned in the enclosure component, whereinthe physiological signal processing module obtains acquisition signalsthrough the physiological signal acquisition interface, converts theacquisition signals into digital signals and obtains the at least oneperipheral circulation parameter through calculation based on thedigital signals; and an interactive interface for interaction with ahost through the interaction and constant component interface.
 9. Thecardio-pulmonary resuscitation (CPR) monitoring device of claim 1,wherein the absolute amplitude value Amp_(CPR) of a single pulse wave inthe fluctuant component is calculated according to the formula,${Amp}_{CPR} = \sqrt{\frac{\sum\limits_{n = 0}^{N - 1}{S_{AC}^{2}(n)}}{N}}$where S_(AC)(n) represents an n^(th) sampling data point of the singlepulse wave in the fluctuant component, and N represents a total samplingpoint count of the single pulse wave in the fluctuant component.
 10. Thecardio-pulmonary resuscitation (CPR) monitoring device of claim 1,wherein the absolute area parameter Area_(CPR) of the single pulse waveis calculated according to the formula,${Area}_{CPR} = {\sum\limits_{n = 0}^{N - 1}{S_{AC}^{2}(n)}}$ whereS_(AC)(n) represents an n^(th) sampling data point of a single pulsewave, and N represents a total sampling point count of the single pulsewave.
 11. A cardio-pulmonary resuscitation (CPR) monitoring device,comprising: a blood oxygen probe to detect blood oxygen signals of atest subject in real time, wherein the blood oxygen probe includes anoptical transceiver comprising: a light emitting tube that emits atleast one light signal; and a receiving tube located with respect to thelight emitting tube to receive the at least one light signal after theat least one light signal has passed through human tissue as at leastone transmission signal through the human tissue and convert the atleast one light signal into at least one electrical signal; a bloodoxygen module, coupled to the blood oxygen probe, wherein the bloodoxygen module acquires the blood oxygen signals outputted from the bloodoxygen probe, generates a pulse oximetry waveform based on the bloodoxygen signals, separates a constant component and a fluctuant componentof the pulse oximetry waveform, calculates one or more peripheralcirculation parameters related to CPR quality based on an effectivefrequency component of the pulse oximetry waveform using frequencydomain analysis, wherein the CPR quality is related to the separatedfluctuant component; and an output module, coupled to the blood oxygenmodule, that outputs the one or more peripheral circulation parametersrelated to CPR quality.
 12. The CPR monitoring device of claim 11,wherein the at least one peripheral circulation parameters include ablood oxygen frequency characteristic of the pulse oximetry waveform andone or more peripheral circulation parameters generated by compression.13. The CPR monitoring device of claim 12, wherein the one or moreperipheral circulation parameters generated by compression includeamplitude characteristic of a single pulse wave.
 14. The CPR monitoringdevice of claim 13, wherein the blood oxygen module also calculates afluctuating value of the amplitude characteristic, evaluates whether thefluctuating value of the amplitude characteristic is less than a firstpreset value and whether the amplitude characteristic falls within anamplitude distribution range limit; and if so, the blood oxygen moduleoutputs a prompt message to inform a user that current compressionquality has reached the standard.
 15. The CPR monitoring device of claim13, wherein the amplitude characteristic includes an absolute amplitudevalue or an amplitude index, wherein the amplitude index is a ratiobetween the absolute amplitude value of single pulse wave of thefluctuant component of an amplified pulse oximetry waveform andcorresponding DC component of the amplified pulse oximetry waveform. 16.The CPR monitoring device of claim 12, wherein the one or moreperipheral circulation parameters generated by compression include anarea characteristic of a single pulse wave.
 17. The CPR monitoringdevice of claim 16, wherein the output module displays at least one of awaveform graph of an amplitude characteristic and an area characteristicon a display interface.
 18. The CPR monitoring device of claim 17,wherein the output module further displays at least one of an amplitudedistribution range limit and an area distribution range limit related toa standard value of chest compression quality on the waveform graph ofat least one of the amplitude characteristic and the areacharacteristic.
 19. The CPR monitoring device of claim 16, wherein theblood oxygen module also calculates a fluctuating value of the areacharacteristic, evaluates whether the fluctuating value of the areacharacteristic is less than a second preset value and whether the areacharacteristic is within an area distribution range limit; and if so,the blood oxygen module outputs a prompt message to inform a user thatcurrent compression quality has reached the standard.
 20. The CPRmonitoring device of claim 16, wherein the area characteristic includesan absolute area value or an area index, wherein the area index is aratio between the absolute area value of single pulse wave of thefluctuant component of an amplified pulse oximetry waveform andcorresponding DC component of the amplified pulse oximetry waveform. 21.The CPR monitoring device of claim 12, wherein the blood oxygen modulecalculates the blood oxygen frequency characteristic and the one or moreperipheral circulation parameters generated by compression based on oneof the fluctuant component of the pulse oximetry waveform and a ratiobetween the fluctuant component and the constant component of the pulseoximetry waveform.
 22. The CPR monitoring device of claim 11, whereinthe CPR quality is related to an absolute amplitude value, AMP_(CPR)^(*), of all frequency components f_(n) (n=1, 2, 3, . . . N) of thefluctuant component, which is calculated according to the formula:${Amp}_{CPR}^{\star} = \sqrt{\frac{\sum\limits_{n = 0}^{N - 1}\left( {\sum\limits_{k = 0}^{K - 1}{X_{f_{n}}(k)}^{2}} \right)}{K}}$where Amp_(CPR) ^(*) represents the absolute amplitude value, krepresents ae sampling data point of a current f_(n), K represents atotal data length of a effective main frequency f_(n), and n representsthe n^(th) frequency peak which amounts to N effective frequency peaks.23. The CPR monitoring device of claim 11, wherein the CPR quality isrelated to an absolute area value, Area_(CPR) ^(*), of all frequencycomponents f_(n) (n=1, 2, 3, . . . N) of the fluctuant component, whichis calculated according to the formula:${Area}_{CPR}^{\star} = {\sum\limits_{n = 0}^{N - 1}\left( {\sum\limits_{k = 0}^{K - 1}{X_{f_{n}}(k)}} \right)}$where Area_(CPR) ^(*) represents an absolute area value of a singlepulse wave, n represents a current effective frequency component f_(n),N represents a total number of the effective frequency components, krepresents a sampling data point of the current effective frequencyf_(n), and K represents a total data length of the effective frequencycomponent f_(n).
 24. A cardio-pulmonary resuscitation (CPR) monitoringmethod, comprising: emitting at least one light signal into human tissuevia a light emitting tube; receiving, via a receiving tube located withrespect to the light emitting tube, the at least one light signal afterthe at least one light signal has passed through the human tissue as atleast one transmission signal through the human tissue; converting theat least one light signal into at least one electrical signal;converting the at least one electrical signal into at least one digitalsignal including a real-time pulsatile perfusion characteristic;processing the at least one digital signal to obtain at least oneperipheral circulation parameter related to CPR quality, wherein thereal-time pulsatile perfusion characteristic is obtained by separating afluctuant component and a constant component of the at least one digitalsignal, and wherein the CPR quality is related to at least one of anabsolute amplitude value or an absolute area value of at least onesingle pulse wave in the separated fluctuant component, wherein eachsingle pulse wave is measured from a wave trough to an adjacent wavecrest; and outputting information corresponding to the at least oneperipheral circulation parameter related to CPR quality.
 25. Acardio-pulmonary resuscitation (CPR) monitoring device, comprising: anoptical transceiver comprising: a light emitting tube that emits atleast one light signal; and a receiving tube located with respect to thelight emitting tube to receive the at least one light signal after theat least one light signal has passed through human tissue as at leastone transmission signal through the human tissue and convert the atleast one light signal into at least one electrical signal; a digitalprocessor to convert the at least one electrical signal into at leastone digital signal reflecting at least one peripheral circulationparameter related to CPR quality; wherein the digital processor obtainsthe at least one peripheral circulation parameter by separating afluctuant component and a constant component of the at least one digitalsignal, and wherein the CPR quality is related to at least one of anabsolute amplitude value or an absolute area value of at least onesingle pulse wave in the separated fluctuant component, wherein eachsingle pulse wave is measured from a wave trough to an adjacent wavecrest, wherein the digital processor processes the at least one digitalsignal using a time domain analysis method, wherein the time domainanalysis method calculates the at least one peripheral circulationparameter by identifying at least one of a frequency characteristic, anamplitude characteristic and an area characteristic of the at least onedigital signal, wherein the time domain analysis method identifies theamplitude characteristic and the area characteristic of the at least onedigital signal based on the fluctuant component of the at least onedigital signal, and wherein the time domain analysis method identifiesthe amplitude characteristic and the area characteristic of the at leastone digital signal based on a ratio between the fluctuant component anda constant component of the at least one digital signal; and an outputmodule to output information corresponding to the at least oneperipheral circulation parameter related to CPR quality.